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  • 1.
    Ahmed, Trifa M.
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of oxygenated and native polycyclic aromatic hydrocarbons in urban dust and diesel particulate matter standard reference materials using pressurized liquid extraction and LC-GC/MS2015In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 407, no 2, p. 427-438Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to develop a novel analytical chemistry method, comprised of a coupled high-performance liquid chromatography-gas chromatography/mass spectrometry system (LC-GC/MS) with low detection limits and high selectivity, for the identification and determination of oxygenated polycyclic aromatic hydrocarbons (OPAHs) and polycyclic aromatic hydrocarbons (PAHs) in urban air and diesel particulate matter. The linear range of the four OPAHs, which include 9,10-anthraquinone, 4H-cyclopenta[def]phenanthrene-4-one, benzanthrone, and 7,12-benz[a]anthraquinone, was 0.7 pg-43.3 ng with limits of detection (LODs) and limits of quantification (LOQs) on the order of 0.2-0.8 and 0.7-1.3 pg, respectively. The LODs in this study are generally lower than values reported in the literature, which can be explained by using large-volume injection. The recoveries of the OPAHs spiked onto glass fiber filters using two different pressurized liquid extraction (PLE) methods were in the ranges of 84-107 and 67-110 %, respectively. The analytical protocols were validated using the following National Institute of Standards and Technology standard reference materials: SRM 1649a (Urban Dust), SRM 1650b (Diesel Particulate Matter), and SRM 2975 (Diesel Particulate Matter, Industrial Forklift). The measured mass fractions of the OPAHs in the standard reference materials (SRMs) in this present study are higher than the values from the literature, except for benzanthrone in SRM 1649a (Urban Dust). In addition to the OPAHs, 44 PAHs could be detected and quantified from the same particulate extract used in this protocol. Using data from the literature and applying a two-sided t test at the 5 % level using Bonferroni correction, significant differences were found between the tested PLE methods for individual PAHs. However, the measured mass fractions of the PAHs were comparable, similar to, or higher than those previously reported in the literature.

  • 2.
    Ahmed, Trifa M.
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Lim, Hwanmi
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Automated clean-up, separation and detection of polycyclic aromatic hydrocarbons in particulate matter extracts from urban dust and diesel standard reference materials using a 2D-LC/2D-GC system2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 25, p. 8215-8222Article in journal (Refereed)
    Abstract [en]

    A multidimensional, on-line coupled liquid chromatographic/gas chromatographic system was developed for the quantification of polycyclic aromatic hydrocarbons (PAHs). A two-dimensional liquid chromatographic system (2D-liquid chromatography (LC)), with three columns having different selectivities, was connected on-line to a two-dimensional gas chromatographic system (2D-gas chromatography (GC)). Samples were cleaned up by combining normal elution and column back-flush of the LC columns to selectively remove matrix constituents and isolate well-defined, PAH enriched fractions. Using this system, the sequential removal of polar, mono/diaromatic, olefinic and alkane compounds from crude extracts was achieved. The LC/GC coupling was performed using a fused silica transfer line into a programmable temperature vaporizer (PTV) GC injector. Using the PTV in the solvent vent mode, excess solvent was removed and the enriched PAH sample extract was injected into the GC. The 2D-GC setup consisted of two capillary columns with different stationary phase selectivities. Heart-cutting of selected PAH compounds in the first GC column (first dimension) and transfer of these to the second GC column (second dimension) increased the baseline resolutions of closely eluting PAHs. The on-line system was validated using the standard reference materials SRM 1649a (urban dust) and SRM 1975 (diesel particulate extract). The PAH concentrations measured were comparable to the certified values and the fully automated LC/GC system performed the clean-up, separation and detection of PAHs in 16 extracts in less than 24 h. The multidimensional, on-line 2D-LC/2D-GC system eliminated manual handling of the sample extracts and minimised the risk of sample loss and contamination, while increasing accuracy and precision.

  • 3.
    Aldaeus, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thewalim, Yasar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Prediction of retention times of polycyclic aromatic hydrocarbons and n -alkanes in temperature-programmed gas chromatography2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 389, no 3, p. 941-950Article in journal (Refereed)
    Abstract [en]

    We have developed an iterative procedure for predicting the retention times of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes during separations by temperature-programmed gas chromatography. The procedure is based on estimates of two thermodynamic properties for each analyte (the differences in enthalpy and entropy associated with movements between the stationary and mobile phases) derived from data acquired experimentally in separations under isothermal conditions at temperatures spanning the range covered by the temperature programs in ten-degree increments. The columns used for this purpose were capillary columns containing polydimethylsiloxane-based stationary phases with three degrees of phenyl substitution (0%, 5%, and 50%). Predicted values were mostly within 1% of experimentally determined values, implying that the method is stable and precise.

  • 4.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bro, Rasmus
    Engelsen, Sören B.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Vibrational overtone combination spectroscopy (VOCSY)—a new way of using IR and NIR data2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 388, no 1, p. 179-188Article in journal (Refereed)
    Abstract [en]

    This work explores a novel method for rearranging 1st order (one-way) infra-red (IR) and/or near infra-red (NIR) ordinary spectra into a representation suitable for multi-way modelling and analysis. The method is based on the fact that the fundamental IR absorption and the first, second, and consecutive overtones of NIR absorptions represent identical chemical information. It is therefore possible to rearrange these overtone regions of the vectors comprising an IR and NIR spectrum into a matrix where the fundamental, 1st, 2nd, and consecutive overtones of the spectrum are arranged as either rows or columns in a matrix, resulting in a true three-way tensor of data for several samples. This tensorization facilitates explorative analysis and modelling with multi-way methods, for example parallel factor analysis (PARAFAC), N-way partial least squares (N-PLS), and Tucker models. The vibrational overtone combination spectroscopy (VOCSY) arrangement is shown to benefit from the “order advantage”, producing more robust, stable, and interpretable models than, for example, the traditional PLS modelling method. The proposed method also opens the field of NIR for true peak decomposition—a feature unique to the method because the latent factors acquired using PARAFAC can represent pure spectral components whereas latent factors in principal component analysis (PCA) and PLS usually do not.

  • 5.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Slagbrand, Tove
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Wahlström, Erik
    Gustafsson, Ingela
    Lindberg, Johan
    Automated annotation and quantification of metabolites in (1)H NMR data of biological origin2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 403, no 2, p. 443-455Article in journal (Refereed)
    Abstract [en]

    In 1H NMR metabolomic datasets, there are often over a thousand peaks per spectrum, many of which change position drastically between samples. Automatic alignment, annotation, and quantification of all the metabolites of interest in such datasets have not been feasible. In this work we propose a fully automated annotation and quantification procedure which requires annotation of metabolites only in a single spectrum. The reference database built from that single spectrum can be used for any number of 1H NMR datasets with a similar matrix. The procedure is based on the generalized fuzzy Hough transform (GFHT) for alignment and on Principal-components analysis (PCA) for peak selection and quantification. We show that we can establish quantities of 21 metabolites in several 1H NMR datasets and that the procedure is extendable to include any number of metabolites that can be identified in a single spectrum. The procedure speeds up the quantification of previously known metabolites and also returns a table containing the intensities and locations of all the peaks that were found and aligned but not assigned to a known metabolite. This enables both biopattern analysis of known metabolites and data mining for new potential biomarkers among the unknowns.

  • 6.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Schuppe-Koistinen, Ina
    Lindberg, Johan
    A solution to the 1D NMR alignment problem using an extended generalized fuzzy Hough transform and mode support2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 395, no 1, p. 213-223Article in journal (Refereed)
    Abstract [en]

    This paper approaches the problem of intersample peak correspondence in the context of later applying statistical data analysis techniques to 1D 1H-nuclear magnetic resonance (NMR) data. Any data analysis methodology will fail to produce meaningful results if the analyzed data table is not synchronized, i.e., each analyzed variable frequency (Hz) does not originate from the same chemical source throughout the entire dataset. This is typically the case when dealing with NMR data from biological samples. In this paper, we present a new state of the art for solving this problem using the generalized fuzzy Hough transform (GFHT). This paper describes significant improvements since the method was introduced for NMR datasets of plasma in Csenki et al. (Anal Bioanal Chem 389:875-885, 15) and is now capable of synchronizing peaks from more complex datasets such as urine as well as plasma data. We present a novel way of globally modeling peak shifts using principal component analysis, a new algorithm for calculating the transform and an effective peak detection algorithm. The algorithm is applied to two real metabonomic 1H-NMR datasets and the properties of the method are compared to bucketing. We implicitly prove that GFHT establishes the objectively true correspondence. Desirable features of the GFHT are: (1) intersample peak correspondence even if peaks change order on the frequency axis and (2) the method is symmetric with respect to the samples.

  • 7.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Schuppe-Koistinen, Ina
    Lindberg, Johan
    Time-resolved biomarker discovery inH-NMR data using generalized fuzzy Hough transform alignment and parallel factor analysis2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 396, no 5, p. 1681-1689Article in journal (Refereed)
    Abstract [en]

    This work addresses the subject of time-series analysis of comprehensive 1H-NMR data of biological origin. One of the problems with toxicological and efficacy studies is the confounding of correlation between the administered drug, its metabolites and the systemic changes in molecular dynamics, i.e., the flux of drug-related molecules correlates with the molecules of system regulation. This correlation poses a problem for biomarker mining since this confounding must be untangled in order to separate true biomarker molecules from dose-related molecules. One way of achieving this goal is to perform pharmacokinetic analysis. The difference in pharmacokinetic time profiles of different molecules can aid in the elucidation of the origin of the dynamics, this can even be achieved regardless of whether the identity of the molecule is known or not. This mode of analysis is the basis for metabonomic studies of toxicology and efficacy. One major problem concerning the analysis of 1H-NMR data generated from metabonomic studies is that of the peak positional variation and of peak overlap. These phenomena induce variance in the data, obscuring the true information content and are hence unwanted but hard to avoid. Here, we show that by using the generalized fuzzy Hough transform spectral alignment, variable selection, and parallel factor analysis, we can solve both the alignment and the confounding problem stated above. Using the outlined method, several different temporal concentration profiles can be resolved and the majority of the studied molecules and their respective fluxes can be attributed to these resolved kinetic profiles. The resolved time profiles hereby simplifies finding true biomarkers and bio-patterns for early detection of biological conditions as well as providing more detailed information about the studied biological system. The presented method represents a significant step forward in time-series analysis of biological 1H-NMR data as it provides almost full automation of the whole data analysis process and is able to analyze over 800 unique features per sample. The method is demonstrated using a 1H-NMR rat urine dataset from a toxicology study and is compared with a classical approach: COW alignment followed by bucketing.

  • 8.
    Andrys, Rudolf
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Charles University Prague, Czech Republic .
    Zurita, Javier
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Zguna, Nadezda
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Verschueren, Klaas
    De Borggraeve, Wim M.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Improved detection of beta-N-methylamino-L-alanine using N-hydroxysuccinimide ester of N-butylnicotinic acid for the localization of BMAA in blue mussels (Mytilus edulis)2015In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 407, no 13, p. 3743-3750Article in journal (Refereed)
    Abstract [en]

    beta-N-Methylamino-l-alanine (BMAA) is an important non-protein amino acid linked to neurodegenerative diseases, specifically amyotrophic lateral sclerosis (ALS). Because it can be transferred and bioaccumulated higher up the food chain, it poses significant public health concerns; thus, improved detection methods are of prime importance for the identification and management of these toxins. Here, we report the successful use of N-hydroxysuccinimide ester of N-butylnicotinic acid (C-4-NA-NHS) for the efficient separation of BMAA from its isomers and higher sensitivity in detecting BMAA compared to the current method of choice using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatization. Implementation of this efficient method allowed localization of BMAA in the non-visceral tissues of blue mussels, suggesting that more efficient depuration may be required to remove this toxin prior to consumption. This is a crucial method in establishing the absence or presence of the neurotoxic amino acid BMAA in food, environmental or biomedical samples.

  • 9.
    Avagyan, Rozanna
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Nyström, Robin
    Boman, Christoffer
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Determination of hydroxylated polycyclic aromatic hydrocarbons by HPLC-photoionization tandem mass spectrometry in wood smoke particles and soil samples2015In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 407, no 16, p. 4523-4534Article in journal (Refereed)
    Abstract [en]

    A simple and fast method for analysis of hydroxylated polycyclic aromatic hydrocarbons using pressurized liquid extraction and high performance liquid chromatography utilizing photoionization tandem mass spectrometry was developed. Simultaneous separation and determination of nine hydroxylated polycyclic aromatic hydrocarbons and two hydroxy biphenyls could be performed in negative mode with a run time of 12 min, including equilibration in 5 min. The calibration curves were in two concentration ranges; 1-50 ng/mL and 0.01-50 mu g/mL, with coefficients of correlation R (2) > 0.997. The limits of detection and method quantification limits were in the range of 9-56 pg and 5-38 ng/g, respectively. A two-level full factorial experimental design was used for screening of conditions with the highest impact on the extraction. The extraction procedure was automated and suitable for a large number of samples. The extraction recoveries ranged from 70 to 102 % and the matrix effects were between 92 and 104 %. The overall method was demonstrated on wood smoke particles and soil samples with good analytical performance, and five OH-PAHs were determined in the concentration range of 0.19-210 mu g/g. As far as we know, hydroxylated polycyclic aromatic hydrocarbons were determined in wood smoke and soil samples using photoionization mass spectrometry for the first time in this present study. Accordingly, this study shows that high performance liquid chromatography photoionization tandem mass spectrometry can be a good option for the determination of hydroxylated polycyclic aromatic hydrocarbons in complex environmental samples.

  • 10.
    Axelsson, Sara
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Eriksson, Kåre
    Department of Occupational and Environmental Medicine, University Hospital of Northern Sweden, Umeå, Sweden.
    Hagström, Katja
    Department of Environmental Science, Örebro University, Örebro.
    Bryngelsson, Ing-Liss
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    HPLC/neg-ESI-MS determination of resin acids in urine from Swedish wood pellets production plants workers and correlation with air concentrations2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650Article in journal (Refereed)
  • 11.
    Berger, Urs
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kaiser, Mary A.
    Karrman, Anna
    Barber, Jonathan L.
    van Leeuwen, Stefan P. J.
    Recent developments in trace analysis of poly- and perfluoroalkyl substances2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 400, no 6, p. 1625-1635Article in journal (Refereed)
    Abstract [en]

    Recent developments, improvements, and trends in the ultra-trace determination of per- and polyfluoroalkyl substances (PFASs) in environmental and human samples are highlighted and the remaining challenges and uncertainties are outlined and discussed. Understanding the analytical implications of such things as adsorption of PFASs to surfaces, effects of differing matrices, varying PFAS isomer response factors, potential bias effects of sampling, sample preparation, and analysis is critical to measuring highly fluorinated compounds at trace levels. These intricate analytical issues and the potential consequences of ignoring to deal with them correctly are discussed and documented with examples. Isomer-specific analysis and the development of robust multi-chemical methods are identified as topical trends in method development for an ever-increasing number of PFASs of environmental and human interest. Ultimately, the state-of-the-art of current analytical method accuracy is discussed on the basis of results from interlaboratory comparison studies.

  • 12.
    Bergh, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Luongo, Giovanna
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Wise, Stephen
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Organophosphate and phthalate esters in standard reference material 2585 organic contaminants in house dust2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 402, no 1, p. 51-59Article in journal (Refereed)
    Abstract [en]

    The levels of 22 phthalate diesters (phthalates) and organophosphate triesters (organophosphates) have been investigated in standard reference material 2585 (SRM 2585) "organic contaminants in house dust." Ultrasonic-assisted solvent extraction and solid-phase extraction on a Florisil adsorbent were used as the extraction and cleanup steps combined with analysis using gas chromatography-tandem mass spectrometry in positive ion chemical ionization mode. Seven phthalates were detected in the concentration range 1-570 mu g/g. Di(2-ethylhexyl) phthalate was the major phthalate present at 570 mu g/g. Ten organophosphates were detected in SRM 2585. Tris(2-butoxyethyl) phosphate was the predominant organophosphate at 82 mu g/g, and nine organophosphates were determined at concentrations ranging from 0.19 to 2.3 mu g/g. Five organophosphates were below the method detection limit, of which two were in level with the procedural blank. The applied extraction and cleanup method was evaluated for the analysis of SRM 2585. The extraction yield was a parts per thousand yen99%, except for tris(2-chloroethyl) phosphate (97%) and diethyl phthalate (98.5%). The problem of calibration curvature is addressed, and it is shown that the use of deuterated standards improves the analysis. The concentrations of ten organophosphate esters were determined in SRM 2585, and seven of these were compared with existing data. To our knowledge, this is the first report of the levels of the seven phthalates esters in SRM 2585 "organic contaminants in house dust.

  • 13.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of dibenzopyrenes in standard reference materials (SRM) 1649a, 1650, and 2975 using ultrasonically assisted extraction and LC-GC-MS2006In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 384, no 2, p. 438-447Article in journal (Refereed)
    Abstract [en]

    A method has been developed for analysis of the highly potent polycyclic aromatic hydrocarbon (PAH) carcinogens dibenzo(a,l)pyrene, dibenzo(a,h)pyrene and dibenzo(a,i)pyrene (molecular weight 302) present in small amounts in diesel and air particulate materials. The method can also be used for analysis of the PAH benzo(a)pyrene, coronene and perylene, for which reference and certified values are available for the Standard Reference Materials used for validation of the method: SRM 1649a (Urban dust) and SRM 2975 (Diesel particulate matter). The only NIST values that have been published for these dibenzopyrene isomers in the analyzed SRMs are reference values for dibenzo(a,i)pyrene and dibenzo(a,h)pyrene in SRM 1649a. The concentrations determined in the SRMs were in good agreement with reported NIST-certified and reference values and other concentrations reported in the literature. The Standard Reference Material 1650 (Diesel particulate matter) was also analyzed. The method could not, however, be validated using this material because certification of SRM 1650 had expired. The method is based on ultrasonically-assisted extraction of the particulate material, then silica SPE pre-separation and isolation, and, separation and detection by hyphenated LC-GC-MS. The method is relatively rapid and requires only approximately 1-5 mg SRM particulate material to identify and quantify the analytes. Low extraction recoveries for the analytes, in particular the dibenzopyrenes, when extracting diesel SRMs 2975 and 1650 resulted, however, in the dibenzopyrenes being present in amounts near their limit of quantifications in these samples. The method’s limit of quantification (LOQ), based on analyses of SRM 1649a, is in the range of 10-77 pg. By use of this method more than 25 potential PAH isomers with a molecular weight of 302 could be separated.

  • 14.
    Bergvall, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of 252-302 Da and tentative identification of 316-376 Da polycyclic aromatic hydrocarbons in Standard Reference Materials 1649a Urban Dust and 1650b and 2975 Diesel Particulate Matter by accelerated solvent extraction-HPLC-GC-MS.2008In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 391, no 6, p. 2235-2248Article in journal (Refereed)
    Abstract [en]

    We have assessed and compared the extraction recoveries of polycyclic aromatic hydrocarbons (PAHs) with molecular weights of 252, 276, 278, 300 and 302 from diesel particulate matter (PM) and urban air particles using ultrasonically-assisted extraction and accelerated solvent extraction methods, and evaluated the effects of sample and treatment parameters. The results show that accelerated solvent extraction can extract PAHs more efficiently from diesel PM than ultrasonically assisted extraction. They also show that PAHs are more difficult to extract from diesel PM than from urban air particles. Using toluene and maximum instrumental settings (200 ºC, 3000 psi and five extraction cycles) with 30 min static extraction times > 85 % of the analytes were estimated to be extracted from the diesel particles, but four extraction cycles with just 5 min static extraction times under these conditions seems to be sufficient to extract > 95 % of the analytes from the urban air particles. The accelerated solvent extraction method was validated using Standard Reference Materials (SRM) 1649a, Urban Dust, SRM 2975 and SRM 1650a, Diesel Particulate Matter, from the US National Institute of Standards and Technology (NIST). PAH concentrations determined by on-line high performance liquid chromatography-gas chromatography-mass spectrometry following the developed accelerated solvent extraction method were generally higher than the certified and reference NIST values and concentrations reported in the literature (e.g. the estimated concentration of benzo(a)pyrene in SRM 2975 was 15-fold higher than the NIST-certified value), probably because the extraction recoveries were higher than in previous studies. The developed accelerated solvent extraction method was used to analyze high molecular weight PAHs (Mw>302) in the investigated SRMs, and more than 170 (SRM 1649a), 80 (SRM 1650b) and 60 (SRM 2975) potential high molecular weight PAHs were tentatively identified in them, with molecular weights (depending on the SRM sample analysed) of 316, 326, 328, 340, 342, 350, 352, 366, 374 and 376. This is, to our knowledge, the first study to tentatively report PAHs with molecular weights of 316, 326, 328, 342, 350, 352, 366 and 374 in diesel particulate matter. GC-MS chromatograms obtained in selected ion monitoring mode (extracted ions for the above mentioned m/z) and full-scan mass spectra of tentatively identified high molecular weight PAHs are shown in the electronical supplementary material.

  • 15. Campone, Luca
    et al.
    Piccinelli, Anna Lisa
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Rastrelli, Luca
    Determination of organophosphorous flame retardants in fish tissues by matrix solid-phase dispersion and gas chromatography2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650Article in journal (Refereed)
  • 16.
    Csenki, Leonard
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Alm, Erik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nord, Lars I.
    Schuppe-Koistinen, Ina
    Lindberg, Johan
    Proof of principle of a generalized fuzzy Hough transform approach to peak alignment of one-dimensional 1H NMR data2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 389, no 3, p. 875-885Article in journal (Refereed)
    Abstract [en]

    In metabolic profiling, multivariate data analysis techniques are used to interpret one-dimensional (1D) 1H NMR data. Multivariate data analysis techniques require that peaks are characterised by the same variables in every spectrum. This location constraint is essential for correct comparison of the intensities of several NMR spectra. However, variations in physicochemical factors can cause the locations of the peaks to shift. The location prerequisite may thus not be met, and so, to solve this problem, alignment methods have been developed. However, current state-of-the-art algorithms for data alignment cannot resolve the inherent problems encountered when analysing NMR data of biological origin, because they are unable to align peaks when the spatial order of the peaks changes—a commonly occurring phenomenon. In this paper a new algorithm is proposed, based on the Hough transform operating on an image representation of the NMR dataset that is capable of correctly aligning peaks when existing methods fail. The proposed algorithm was compared with current state-of-the-art algorithms operating on a selected plasma dataset to demonstrate its potential. A urine dataset was also processed using the algorithm as a further demonstration. The method is capable of successfully aligning the plasma data but further development is needed to address more challenging applications, for example urine data.

  • 17.
    Fyrestam, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bjurshammar, Nadja
    Paulsson, Elin
    Johannsen, Annsofi
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Determination of porphyrins in oral bacteria by liquid chromatography electrospray ionization tandem mass spectrometry2015In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 407, no 23, p. 7013-7023Article in journal (Refereed)
    Abstract [en]

    Biofilms in the oral cavity can be visualized by fluorescence and a common assumption is that the endogenously produced porphyrins in certain bacteria give rise to this fluorescence. Porphyrin content in oral bacteria has been sparingly investigated, and non-selective detection techniques such as utilizing the Soret fluorescence band of porphyrins are often used. In the present study, a quantitative and selective method for the determination of porphyrins in oral bacteria has been developed and validated using high performance liquid chromatography-tandem mass spectrometry. Lysis of bacteria using Tris-EDTA buffer together with ultrasonication showed high microbial killing efficiency ≥99.98 %, and sample clean-up using C18-solid phase extraction resulted in low matrix effects ≤14 % for all analytes. Using this method, the porphyrin content was determined in the two oral pathogens Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, as well as for baker’s yeast, Saccharomyces cerevisiae. Uroporphyrin, 7-carboxylporphyrin, 6-carboxylporphyrin, coproporphyrin, and protoporphyrin IX were identified in the investigated microorganisms, and it was shown that the porphyrin profile differs between the two bacteria, as well as for S. cerevisiae. To our knowledge, this is the first time the porphyrin profile has been determined for the bacterium A. actinomycetemcomitans.

  • 18.
    Fyrestam, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Determination of heme in microorganisms using HPLC-MS/MS and cobalt(III) protoporphyrin IX inhibition of heme acquisition in Escherichia coli2017In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 409, no 30, p. 6999-7010Article in journal (Refereed)
    Abstract [en]

    One of the main threats to the achievements in modern medicine is antimicrobial resistance. Molecular targeting of bacterial acquisition mechanisms of heme has been suggested to be an alternative to antibiotics. In the present study, HPLC-MS/MS combined with a simple clean-up based on liquid-liquid extraction has been developed and evaluated for simultaneous determination of heme and porphyrin heme precursors in microorganisms. Experimental design was used to optimize the extraction parameters, to obtain a method with high recovery, low matrix effects, and high precision. The effects of additives in the culture medium on the biosynthesis of heme were studied using Escherichia coli as a model microorganism. 5-Aminolaevulinic acid and hemin increased the heme concentration in E. coli by a factor of 1.5 and 4.5, respectively. Addition of 5-aminolaevulinic acid bypassed the E. coli negative feedback control of heme biosynthesis, which led to high amounts of intracellular porphyrins. The high heme concentration obtained when hemin was used as a culture additive shows that E. coli has an uptake of heme from its surroundings. In contrast, addition of cobalt protoporphyrin IX to the growth medium reduced the amount of heme in E. coli, demonstrating this compound’s ability to mimic real heme and inhibit the heme acquisition mechanisms.

  • 19.
    Gao, Qiuju
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Monosaccharide compositional analysis of marine polysaccharides by hydrophilic interaction liquid chromatography-tandem mass spectrometry2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 7, p. 2517-2529Article in journal (Refereed)
    Abstract [en]

    A simple and sensitive method was developed using hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry for determination of monosaccharides liberated from marine polysaccharides by acidic hydrolysis. Optimal separation of diastereomeric monosaccharides including hexoses, pentoses, and deoxyhexoses was achieved using an aminopropyl bonded column with mobile phase containing ternary solvents (acetonitrile/methanol/water) in conjunction with MS/MS in SRM mode. Mechanisms for fragmentation of deprotonated monosaccharides with regard to cross-ring cleavage were proposed. Matrix effects from coeluting interferences were observed and isotopic-labeled internal standard was used to compensate for the signal suppression. The method demonstrated excellent instrumental limits of detection (LOD), ranging from 0.7 to 4.2 pg. Method LODs range from 0.9 to 5.1 nM. The proposed method was applied to the analysis of polysaccharides in seawater collected from the open leads of the central Arctic Ocean in the summer of 2008.

  • 20. Horvai, George
    et al.
    Worsfold, Paul
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, Jens E. T.
    European analytical column no. 392011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 400, no 6, p. 1539-1541Article in journal (Refereed)
  • 21.
    Isetun, Sindra
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of solid-phase microextraction with PDMS for air sampling of gaseous organophosphate flame-retardants and plasticizers2004In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 380, no 2, p. 319-324Article in journal (Refereed)
    Abstract [en]

    As an inexpensive, simple, and low-solvent consuming extraction technique, the suitability of solid-phase microextraction (SPME) with polydimethylsiloxane (PDMS) sorbent was investigated as a quantitative method for sampling gaseous organophosphate triesters in air. These compounds have become ubiquitous in indoor air, because of their widespread use as additive flame retardants/plasticizers in various indoor materials. Results obtained by sampling these compounds at controlled air concentrations using SPME and active sampling on glass fibre filters were compared to evaluate the method. A constant linear airflow of 10 cm s–1 over the fibres was applied to increase the extraction rate. For extraction of triethyl phosphate with a 100-m PDMS fibre, equilibrium was achieved after 8 h. The limit of detection was determined to be less than 10 pg m–3. The PDMS–air partition coefficients, Kfs, for the individual organophosphate triesters were determined to be in the range 5–60×106 at room temperature (22–23°C). Air measurements were performed utilising the determined coefficients for quantification. In samples taken from a lecture room four different airborne organophosphate esters were identified, the most abundant of which was tris(chloropropyl) phosphate, at the comparatively high level of 1.1 g m–3. The results from SPME and active sampling had comparable repeatability (RSD less than 17%), and the determined concentrations were also similar. The results suggest that the investigated compounds were almost entirely associated with the gaseous phase at the time and place sampled.

  • 22.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Aigret, Benoit
    De Borggraeve, Wim M.
    Spacil, Zdenek
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Selective LC-MS/MS method for the identification of BMAA from its isomers in biological samples2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 403, no 6, p. 1719-1730Article in journal (Refereed)
    Abstract [en]

    Algal blooms are well-known sources of acute toxic agents that can be lethal to aquatic organisms. However, one such toxin, beta--methylamino--alanine (BMAA) is also believed to cause amyotrophic lateral sclerosis, also known as Lou Gehrig's disease. The detection and identification of BMAA in natural samples were challenging until the recent introduction of reliable methods. However, the issue of potential interference from unknown isomers of BMAA present in samples has not yet been thoroughly investigated. Based on a systematic database search, we generated a list of all theoretical BMAA structural isomers, which was subsequently narrowed down to seven possible interfering compounds for further consideration. The seven possible candidates satisfied the requirements of chemical stability and also shared important structural domains with BMAA. Two of the candidates, 2,4-diaminobutyric acid (DAB) and -(2-aminoethyl) glycine (AEG) have recently been studied in the context of BMAA. A further isomer, beta-amino--methyl-alanine (BAMA), has to be considered because it can potentially yield the fragment ion, which is diagnostic for BMAA. Here, we report the synthesis and analysis of BAMA, together with AEG, DAB, and other isomers that are of interest in the separation and detection of BMAA in biological samples by using either high-performance liquid chromatography or ultra-high-performance liquid chromatography coupled with tandem mass spectrometry. We detected for the first time BAMA in blue mussel and oyster samples. This work extends the previously developed liquid chromatography-tandem mass spectrometry platform Spacil et al. (Analyst 135:127, 2010) to allow BMAA isomers to be distinguished, improving the detection and identification of this important amino acid.

  • 23.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Strategy for quantifying trace levels of BMAA in cyanobacteria by LC/MS/MS2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 4, p. 1283-1292Article in journal (Refereed)
    Abstract [en]

    The cyanobacterial neurotoxin β-N-methylamino--alanine (BMAA) is an amino acid that is putatively associated with the pathology of amyotrophic lateral sclerosis/Parkinsonism –dementia complex (ALS-PDC) disease. It raises serious health risk concerns since cyanobacteria are ubiquitous thus making human exposure almost inevitable. The identification and quantification of BMAA in cyanobacteria is challenging because it is present only in trace amounts and occurs alongside structurally similar compounds such as BMAA isomers. This work describes an enhanced liquid chromatography/tandem mass spectrometry platform that can distinguish BMAA from its isomers β-amino-N-methyl-alanine, N-(2-oethyl) glycine (AEG), and 2,4-diaminobutyric acid, thus ensuring confident identification of BMAA. The method's sensitivity was improved fourfold by a post-column addition of acetonitrile. The instrument and method limits of detection were shown to be 4.2 fmol/injection (or 0.5 g/one column) and 0.1 μg/g dry weight of cyanobacteria, respectively. The quantification method uses synthesized deuterated BMAA as an internal standard and exhibits good linearity, accuracy, and precision. Matrix effects were also investigated, revealing an ion enhancement of around 18 %. A lab-cultured cyanobacterial sample (Leptolyngbya PCC73110) was analyzed and shown to contain about 0.73 μg/g dry weight BMAA. The isomer AEG, whose chromatographic properties closely resemble those of BMAA, was also detected. These results highlight the importance of distinguishing BMAA from its isomers for reliable identification as well as providing a sensitive and accurate quantification method for measuring trace levels of BMAA in cyanobacterial samples.

  • 24.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Emons, Hendrik
    Andersen, Jens E. T.
    European analytical column No. 36 (January 2008)2008In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 391, no 4, p. 1109-1112Article in journal (Refereed)
  • 25.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Korte, Ernst-Heiner
    European Analytical Column No. 35 (January 2007)2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 388, no 3, p. 513-515Article in journal (Refereed)
  • 26.
    Kolmert, J.
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Forngren, B.
    Lindberg, J.
    Ohd, J.
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, G.
    Moritz, T.
    Nordström, A.
    A quantitative LC/MS method targeting urinary 1-methyl-4-imidazoleacetic acid for safety monitoring of the global histamine turnover in clinical studies2014In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 6, p. 1751-1762Article in journal (Refereed)
    Abstract [en]

    Anaphylaxis is a potentially life-threatening condition triggered mainly by the release of inflammatory mediators, notably histamine. In pharmaceutical research, drug discovery, and clinical evaluation, it may be necessary to accurately assess the potential of a compound, event, or disorder to promote the release of histamine. In contrast to the measurement of plasma histamine, determination of the stable metabolite 1-methyl-4-imidazoleacetic acid (tele-MIAA) in urine provides a noninvasive and more reliable methodology to monitor histamine release. This study presents a repeatable high-performance liquid chromatography coupled to electrospray mass spectrometry (LC-ESI-MS) method where tele-MIAA is baseline separated from its structural isomer 1-methyl-5-imidazoleacetic acid (pi-MIAA) and an unknown in human urine. The ion-pairing chromatography method, in reversed-phase mode, based on 0.5 mM tridecafluoroheptanoic acid demonstrated high repeatability and was applied in a clinical development program that comprised a large number of clinical samples from different cohorts. The inter- and intra-run precision of the method for tele-MIAA were 8.4 and 4.3 %, respectively, at the mean urinary concentration level, while method accuracy was between -16.2 and 8.0 % across the linear concentration range of 22-1,111 ng mL(-1). Overall, method precision was greater than that reported in previously published methods and enabled the identification of gender differences that were independent of age or demography. The median concentration measured in female subjects was 3.0 mu mol mmol(-1) of creatinine, and for male subjects, it was 2.1 mu mol mmol(-1) of creatinine. The results demonstrate that the method provides unprecedented accuracy, precision, and practicality for the measurement of tele-MIAA in large clinical settings.

  • 27. Kunzelmann, Marco
    et al.
    Winter, Martin
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Hellenäs, Karl-Erik
    Rosén, Johan
    Non-targeted analysis of unexpected food contaminants using LC-HRMS2018In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 410, no 22, p. 5593-5602Article in journal (Refereed)
    Abstract [en]

    A non-target analysis method for unexpected contaminants in food is described. Many current methods referred to as non-target are capable of detecting hundreds or even thousands of contaminants. However, they will typically still miss all other possible contaminants. Instead, a metabolomics approach might be used to obtain true non-target analysis. In the present work, such a method was optimized for improved detection capability at low concentrations. The method was evaluated using 19 chemically diverse model compounds spiked into milk samples to mimic unknown contamination. Other milk samples were used as reference samples. All samples were analyzed with UHPLC-TOF-MS (ultra-high-performance liquid chromatography time-of-flight mass spectrometry), using reversed-phase chromatography and electrospray ionization in positive mode. Data evaluation was performed by the software TracMass 2. No target lists of specific compounds were used to search for the contaminants. Instead, the software was used to sort out all features only occurring in the spiked sample data, i.e., the workflow resembled a metabolomics approach. Procedures for chemical identification of peaks were outside the scope of the study. Method, study design, and settings in the software were optimized to minimize manual evaluation and faulty or irrelevant hits and to maximize hit rate of the spiked compounds. A practical detection limit was established at 25 mu g/kg. At this concentration, most compounds (17 out of 19) were detected as intact precursor ions, as fragments or as adducts. Only 2 irrelevant hits, probably natural compounds, were obtained. Limitations and possible practical use of the approach are discussed.

  • 28.
    Larson, Tuula
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    An automated multidimensional preparative gas chromatographic system for isolation and enrichment of trace amounts of xenon from ambient air2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 400, no 2, p. 449-458Article in journal (Refereed)
    Abstract [en]

    The monitoring of radioactive xenon isotopes is one of the principal methods for the detection of nuclear explosions in order to identify clandestine nuclear testing. In this work, a miniaturized, multiple-oven, six-column, preparative gas chromatograph was constructed in order to isolate trace quantities of radioactive xenon isotopes from ambient air, utilizing nitrogen as the carrier gas. The multidimensional chromatograph comprised preparative stainless steel columns packed with molecular sieves, activated carbon, and synthetic carbon adsorbents (e.g., AnasorbA (R)-747 and CarbosphereA (R)). A combination of purification techniques-ambient adsorption, thermal desorption, back-flushing, thermal focusing, and heart cutting-was selectively optimized to produce a well-defined xenon peak that facilitated reproducible heart cutting and accurate quantification. The chromatographic purification of a sample requires approximately 4 h and provides complete separation of xenon from potentially interfering components (such as water vapor, methane, carbon dioxide, and radon) with recovery and accuracy close to 100%. The preparative enrichment process isolates and concentrates a highly purified xenon gas fraction that is suitable for subsequent ultra-low-level gamma-, /gamma-spectroscopic or high-resolution mass spectrometric measurement (e.g., to monitor the gaseous fission products of nuclear explosions at remote locations). The Xenon Processing Unit is a free-standing, relatively lightweight, and transportable system that can be interfaced to a variety of sampling and detection systems. It has a relatively inexpensive, rugged, and compact modular (19-inch rack) design that provides easy access to all parts for maintenance and has a low power requirement.

  • 29.
    Lim, Hwanmi
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ahmed, Trifa M.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Livsmedelsverket, Sweden.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Uppsala University, Sweden.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Automated clean-up, separation and detection of polycyclic aromatic hydrocarbons in particulate matter extracts using a 2D-LC/2D-GC system: a method translation from two FIDs to two MS detectors2017In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 409, no 24, p. 5619-5629Article in journal (Refereed)
    Abstract [en]

    An online two-dimensional (2D) liquid chromatography/2D gas chromatography system with two mass-selective detectors has been developed on the basis of a previous system with two flame ionization detectors. The method translation involved the change of carrier gas from hydrogen to helium, column dimension and detectors. The 2D system with two mass-selective detectors was validated with use of polycyclic aromatic hydrocarbon (PAH) standards and two standard reference materials from air and diesel exhaust. Furthermore, the system was applied to a real sample, wood smoke particulates. The PAH values determined correlated well with the previous data and those from the National Institute of Standards and Technology. The system enhanced the benefits of the previous system, which were limited by the low detectability and lack of mass selectivity. This study shows an automated 2D system that is valid for PAH analysis of complex environmental samples directly from crude extracts.

  • 30.
    Luongo, Giovanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thorsén, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Quinolines in clothing textiles-a source of human exposure and wastewater pollution?2014In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 12, p. 2747-2756Article in journal (Refereed)
    Abstract [en]

    A production process in which the use of various types of chemicals seems to be ubiquitous makes the textile industry a growing problem regarding both public health as well as the environment. Among several substances used at each stage, the present study focuses on the quinolines, a class of compounds involved in the manufacture of dyes, some of which are skin irritants and/or classified as probable human carcinogens. A method was developed for the determination of quinoline derivatives in textile materials comprising ultrasound-assisted solvent extraction, solid phase extraction cleanup, and final analysis by gas chromatography/mass spectrometry. Quinoline and ten quinoline derivatives were determined in 31 textile samples. The clothing samples, diverse in color, material, brand, country of manufacture, and price, and intended for a broad market, were purchased from different shops in Stockholm, Sweden. Quinoline, a possible human carcinogen, was found to be the most abundant compound present in almost all of the samples investigated, reaching a level of 1.9 mg in a single garment, and it was found that quinoline and its derivatives were mainly correlated to polyester material. This study points out the importance of screening textiles with nontarget analysis to investigate the presence of chemicals in an unbiased manner. Focus should be primarily on clothing worn close to the body.

  • 31.
    Maddalo, Gianluca
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Adams, Christopher M.
    Fung, Eva
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Zubarev, Roman A.
    Sedzik, Jan
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Porcine P2 myelin protein primary structure and bound fatty acids determined by mass spectrometry2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 397, no 5, p. 1903-1910Article in journal (Refereed)
    Abstract [en]

    Complementary collision-induced/electron capture dissociation Fourier-transform ion cyclotron resonance mass spectrometry was used to fully sequence the protein P2 myelin basic protein. It is an antigenic fatty-acid-binding protein that can induce experimental autoimmune neuritis: an animal model of Guillain-Barre syndrome, a disorder similar in etiology to multiple sclerosis. Neither the primary structure of the porcine variant, nor the fatty acids bound by the protein have been well established to date. A 1.8-angstrom crystal structure shows but a bound ligand could not be unequivocally identified. A protocol for ligand extraction from protein crystals has been developed with subsequent gas chromatography MS analysis allowing determination that oleic, stearic, and palmitic fatty acids are associated with the protein. The results provide unique and general evidence of the utility of mass spectrometry for characterizing proteins from natural sources and generating biochemical information that may facilitate attempts to elucidate the causes for disorders such as demyelination.

  • 32.
    Magnér, Jörgen
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Broman, Dag
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bag-SPE – A convenient extraction method for screening of pharmaceutical-residues in influent and effluent water from sewage treatment plants2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 395, no 5, p. 1481-1489Article in journal (Refereed)
    Abstract [en]

    Bag-SPE is a solid phase extraction (SPE) technique here applied to sample pharmaceutical residues in wastewater. The device consisting of 20 mg polystyrene-divinylbenzene (PS-DVB) enclosed in a woven polyester-fabric was immersed into 20 mL sample. Extraction of the analytes was performed under gentle rotation (25 rpm) until distribution equilibrium was achieved (4 hours). The extraction efficiency for thirteen pharmaceuticals was evaluated for the bag-SPE sampler compared to a conventional SPE cartridge (Oasis HLB). All analyzes were determined on an ultra performance liquid chromatography (UPLC) coupled to a quadrupole time of flight (QToF) mass spectrometer.

    The detection limit of the bag-SPE technique for the analytes in wastewater ranged from 15-100 ng/L with recoveries between 20.7-58.2 % and ion-suppressions between 2.2-53.2 %. Although the extraction efficiencies were lower with the bag-SPE sampler compared to the SPE technique, the two methods showed similar detection limits due to the lower ion-suppression experienced with the bag-SPE. The results demonstrate that bag-SPE is an attractive alternative to the more, in terms of manual handling, demanding SPE-technique.

  • 33.
    Magnér, Jörgen
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Broman, Dag
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    The Ability of a Novel Sorptive Polymer to Determine the Freely Dissolved Fraction of Polar Organic Compounds in the Presence of Fulvic Acid or Sediment2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 395, no 5, p. 1525-1532Article in journal (Refereed)
    Abstract [en]

    In the present study, a novel plastic material, poly(ethylene-co-vinyl acetate-co-carbon monoxide) (PEVAC), was evaluated as an absorptive passive equilibrium sampler for determination of the freely dissolved fraction of seven polar organic contaminants (POCs) in the presence of fulvic acid (FA) and sediment. The seven compounds selected were imidacloprid, carbendazim, metoprolol, atrazin, carbamazepine, diazinon and chlorpyrifos, i.e. a mixture of pharmaceuticals and pesticides having logarithmic octanol/water partitioning coefficient (Log KOW) ranging from 0.2 to 4.77.

    The experiments demonstrated that the PEVAC sampler is well suited for determination of the freely dissolved fraction of chemicals in aquatic environments. Generally, the freely dissolved fraction of the POCs decreased with increasing hydrophobicity. However, strong interactions with functional groups of the organic matter seemed to dominate the partitioning for imidacloprid and carbendazim, having logarithmic dissociation partition coefficient (Log D) < 1.47, and for metoprolol which is positively charged at neutral pH.

  • 34.
    Masala, Silvia
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ahmed, Trifa
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Improved efficiency of extraction of polycyclic aromatic hydrocarbons (PAHs) from the National Institute of Standards and Technology (NIST) Standard Reference Material Diesel Particulate Matter (SRM 2975) using accelerated solvent extraction2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 401, no 10, p. 3305-3315Article in journal (Refereed)
    Abstract [en]

    The efficiency of extraction of polycyclic aromatic hydrocarbons (PAHs) with molecular masses of 252, 276, 278, 300, and 302 Da from standard reference material diesel particulate matter (SRM 2975) has been investigated using accelerated solvent extraction (ASE) with dichloromethane, toluene, methanol, and mixtures of toluene and methanol. Extraction of SRM 2975 using toluene/methanol (9:1, v/v) at maximum instrumental settings (200 A degrees C, 20.7 MPa, and five extraction cycles) with 30-min extraction times resulted in the following elevations of the measured concentration when compared with the certified and reference concentrations reported by the National Institute of Standards and Technology (NIST): benzo[b]fluoranthene, 46%; benzo[k]fluoranthene, 137%; benzo[e]pyrene, 103%; benzo[a]pyrene, 1,570%; perylene, 37%; indeno[1,2,3-cd]pyrene, 41%; benzo[ghi]perylene, 163%; and coronene, 361%. The concentrations of the following PAHs were comparable to the reference values assigned by NIST: indeno[1,2,3-cd]fluoranthene, dibenz[a,h]anthracene, and picene. The measured concentration of dibenzo[a,e]-pyrene was lower than the information value reported by the NIST. The measured concentrations of other highly carcinogenic PAHs (dibenzo[a,l]pyrene, dibenzo[a,i]pyrene, and dibenzo[a,h]pyrene) in SRM 2975 are also reported. Comparison of measurements using the optimized ASE method and using similar conditions to those applied by the NIST for the assignment of PAH concentrations in SRM 2975 indicated that the higher values obtained in the present study were associated with more complete extraction of PAHs from the diesel particulate material. Re-extraction of the particulate samples demonstrated that the deuterated internal standards were more readily recovered than the native PAHs, which may explain the lower values reported by the NIST. The analytical results obtained in the study demonstrated that the efficient extraction of PAHs from SRM 2975 is a critical requirement for the accurate determination of PAHs with high molecular masses in this standard reference material and that the optimization of extraction conditions is essential to avoid underestimation of the PAH concentrations. The requirement is especially relevant to the human carcinogen benzo[a]pyrene, which is commonly used as an indicator of the carcinogenic risk presented by PAH mixtures.

  • 35. Metzger, Matthias
    et al.
    Ley, Philip
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sturm, Manfred
    Meermann, Björn
    Screening method for extractable organically bound fluorine (EOF) in river water samples by means of high-resolution-continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS)2019In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 411, no 19, p. 4647-4660Article in journal (Refereed)
    Abstract [en]

    The introduction of fluorine into organic molecules leads to new chemical/physical properties. Especially in the field of pharmaceutical as well as technical applications, fluorinated organic substances gain in importance. The OECD identified and categorized 4730 per- and polyfluoroalkyl substances-related CAS numbers. Thus, an increasing release of fluorinated compounds into the environment is expected. In particular, perfluorinated compounds often show higher environmental stability leading to the risk of bioaccumulation. Polyfluorinated compounds undergo decomposition; thus, further possible fluorine species occur, which may exhibit different toxic/chemical properties. However, current target methods based on, e.g., HPLC/MS-MS, are not applicable for a comprehensive screening of fluorinated substances as well as assessment of pollution. Thus, within this work, a sum parameter method for quantitative determination of extractable organically bound fluorine (EOF) in surface waters was developed. The method is based on solid-phase extraction (SPE) for extraction of fluorinated compounds as well as separation of interfering inorganic fluoride in combination with high-resolution-continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) for organic fluorine quantification. Upon optimization of the SPE procedure (maximum concentration of extractable organic fluorine), enrichment factors of about 1000 were achieved, allowing for highly sensitive fluorine detection. HR-CS GF MAS allows for selective fluorine detection upon in situ formation of a diatomic molecule (GaF). Next to a species-unspecific response, limits of detection in the low nanogram per liter range (upon enrichment) were achieved. Upon successful method development, surface water samples (rivers Moselle and Rhine) were analyzed. Furthermore, a sampling campaign along the river Rhine (from the south-close to the French border; to the north-close to The Netherlands border) was conducted. EOF values in the range of about 50-300ng/L were detected. The developed method allows for a fast and sensitive as well as selective/screening detection of organically bound fluorine (EOF) in surface water samples, helping to elucidate pollution hotspots as well as discharge routes.

  • 36. Mie, Axel
    et al.
    Holst Laursen, Kristian
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Forshed, Jenny
    Lindahl, Anna
    Thorup-Kristensen, Kristian
    Olsson, Marie
    Knuthsen, Pia
    Huusfeldt Larsen, Erik
    Husted, Søren
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Discrimination of conventional and organic white cabbage from a long-term field trial study using untargeted LC-MS-based metabolomics2014In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 12, p. 2885-2897Article in journal (Refereed)
    Abstract [en]

    The influence of organic and conventional farming practices on the content of single nutrients in plants is disputed in the scientific literature. Here, large-scale untargeted LC-MS-based metabolomics was used to compare the composition of white cabbage from organic and conventional agriculture, measuring 1,600 compounds. Cabbage was sampled in 2 years from one conventional and two organic farming systems in a rigidly controlled long-term field trial in Denmark. Using Orthogonal Projection to Latent Structures-Discriminant Analysis (OPLS-DA), we found that the production system leaves a significant (p = 0.013) imprint in the white cabbage metabolome that is retained between production years. We externally validated this finding by predicting the production system of samples from one year using a classification model built on samples from the other year, with a correct classification in 83 % of cases. Thus, it was concluded that the investigated conventional and organic management practices have a systematic impact on the metabolome of white cabbage. This emphasizes the potential of untargeted metabolomics for authenticity testing of organic plant products.

  • 37. Muusse, Martine
    et al.
    Langford, Katherine
    Tollefsen, Knut Erik
    Cornelissen, Gerard
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Haglund, Peter
    Hylland, Ketil
    Thomas, Kevin V.
    Characterization of AhR agonist compounds in roadside snow2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 403, no 7, p. 2047-2056Article in journal (Refereed)
    Abstract [en]

    Aryl hydrocarbon receptor (AhR) agonistic contaminants were identified in roadside snow samples. Snow was collected in Oslo, Norway, and compared to a background sample collected from a mountain area. The water and particulate fractions were analysed for AhR agonists using a dioxin-responsive, chemically activated luciferase expression (CALUX) cell assay and by gas chromatography coupled to high-resolution time-of-flight mass spectrometry with targeted analysis for polycyclic aromatic hydrocarbons (PAHs) and broad-spectrum non-target analysis. The AhR agonist levels in the dissolved fractions in the roadside samples were between 15 and 387 pg/L CALUX toxic equivalents (TEQ(CALUX)). An elevated AhR activity of 221 pg TEQ(CALUX) per litre was detected in the mountain sample. In the particle-bound fractions, the TEQ(CALUX) was between 1,350 and 7,390 pg/L. One possible explanation for the elevated levels in the dissolved fraction of the mountain sample could be the presence of black carbon in the roadside samples, potentially adsorbing dioxin-like compounds and rendering them unavailable for AhR interaction. No polychlorinated dibenzodioxins and dibenzofurans or polychlorinated biphenyls were detected in the samples; the occurrence of PAHs, however, explained up to 9 % of the AhR agonist activity in the samples, whilst comprehensive two-dimensional gas chromatography coupled to mass spectrometry GCxGC-ToF-Ms identified PAH derivatives such as polycyclic aromatic ketones and alkylated, nitrogen sulphur and oxygen PAHs in the particle fractions. The (large) discrepancy between the total and explained activity highlights the fact that there are other as yet unidentified AhR agonists present in the environment.

  • 38.
    Nordqvist, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Colmsjö, Anders
    Investigation of a cylindrical chemosorptive denuder for sampling and phase separation of toluene diisocyanate aerosols2005In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 382, no 5, p. 1294-1299Article in journal (Refereed)
    Abstract [en]

    A cylindrical chemosorptive denuder in series with a glass fibre filter has been evaluated for sampling toluene diisocyanate (TDI) aerosols. The sampler is designed for measuring personal exposure to diisocyanates. Several denuder coatings and derivatising reagents were investigated. Dimethylpolysiloxane (SE-30) and 5% phenyl dimethylpolysiloxane (SE-54) with either dibutylamine (DBA) or dipentylamine (DPeA) as derivatising reagents yielded the lowest vapour breakthrough (the amount (%) of the vapour that passes through the denuder), close to values predicted by theory. Immobilisation of the SE-30 denuder coating by in-situ cross-linking yielded comparable results. With an SE-30/DBA-coated denuder operating within an airflow range of 100–500 mL min<sup>−1</sup>, the phase separation was shown to be consistent with theoretical predictions derived by use of the Gormley–Kennedy equation. This provides a means of calculating the vapour breakthrough and correcting experimentally obtained values with regard to vapour–particulate phase distribution, suggesting that the denuder can provide accurate phase-distribution measurements. The SE-30/DBA denuder can be used over a concentration range spanning nearly six orders of magnitude. Its capacity is sufficient to perform 15-min exposure measurements of a TDI aerosol with air concentrations as high as 1,700 μg m<sup>−3</sup>, 40 times higher than the Swedish occupational exposure limit (OEL). At the other end of the range, the estimated limit of detection (LOD) was less than 2 ng m<sup>−3</sup> for both the vapour and the aerosol phases when LC–ESI–MS–MS was used for chemical analysis.

  • 39.
    Plassmann, Merle M.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Helmholtz Centre for Environmental Research - UFZ, Germany.
    Schmidt, Magdalena
    Brack, Werner
    Krauss, Martin
    Detecting a wide range of environmental contaminants in human blood samples-combining QuEChERS with LC-MS and GC-MS methods2015In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 407, no 23, p. 7047-7054Article in journal (Refereed)
    Abstract [en]

    Exposure to environmental pollution and consumer products may result in an uptake of chemicals into human tissues. Several studies have reported the presence of diverse environmental contaminants in human blood samples. However, previously developed multi-target methods for the analysis of human blood include a fairly limited amount of compounds stemming from one or two related compound groups. Thus, the sample preparation method QuEChERS (quick easy cheap effective rugged and safe) was tested for the extraction of 64 analytes covering a broad compound domain followed by detection using liquid and gas chromatography coupled to mass spectrometry (LC- and GC-MS). Forty-seven analytes showed absolute recoveries above 70 % in the first QuEChERS step, being a simple liquid-liquid extraction (LLE) using acetonitrile and salt. The second QuEChERS step, being a dispersive solid phase extraction, did not result in an overall improvement of recoveries or removal of background signals. Using solely the LLE step, eight analytes could subsequently be detected in human blood samples from the German Environmental Specimen Bank. Using a LC-multiple reaction monitoring (MRM) method with a triple quadrupole instrument, better recoveries were achieved than with an older LC-high-resolution (HR) MS full scan orbitrap instrument, which required a higher concentration factor of the extracts. However, the application of HRMS full scan methods could be used for the detection of additional compounds retrospectively.

  • 40. Rostkowski, Pawel
    et al.
    Haglund, Peter
    Aalizadeh, Reza
    Alygizakis, Nikiforos
    Thomaidis, Nikolaos
    Beltran Arandes, Joaquin
    Nizzetto, Pernilla Bohlin
    Booij, Petra
    Budzinski, Helene
    Brunswick, Pamela
    Covaci, Adrian
    Gallampois, Christine
    Grosse, Sylvia
    Hindle, Ralph
    Ipolyi, Ildiko
    Jobst, Karl
    Kaserzon, Sarit L.
    Leonards, Pim
    Lestremau, Francois
    Letzel, Thomas
    Magner, Jorgen
    Matsukami, Hidenori
    Moschet, Christoph
    Oswald, Peter
    Plassmann, Merle
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Slobodnik, Jaroslav
    Yang, Chun
    The strength in numbers: comprehensive characterization of house dust using complementary mass spectrometric techniques2019In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 411, no 10, p. 1957-1977Article in journal (Refereed)
    Abstract [en]

    Untargeted analysis of a composite house dust sample has been performed as part of a collaborative effort to evaluate the progress in the field of suspect and nontarget screening and build an extensive database of organic indoor environment contaminants. Twenty-one participants reported results that were curated by the organizers of the collaborative trial. In total, nearly 2350 compounds were identified (18%) or tentatively identified (25% at confidence level 2 and 58% at confidence level 3), making the collaborative trial a success. However, a relatively small share (37%) of all compounds were reported by more than one participant, which shows that there is plenty of room for improvement in the field of suspect and nontarget screening. An even a smaller share (5%) of the total number of compounds were detected using both liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). Thus, the two MS techniques are highly complementary. Most of the compounds were detected using LC with electrospray ionization (ESI) MS and comprehensive 2D GC (GCxGC) with atmospheric pressure chemical ionization (APCI) and electron ionization (EI), respectively. Collectively, the three techniques accounted for more than 75% of the reported compounds. Glycols, pharmaceuticals, pesticides, and various biogenic compounds dominated among the compounds reported by LC-MS participants, while hydrocarbons, hydrocarbon derivatives, and chlorinated paraffins and chlorinated biphenyls were primarily reported by GC-MS participants. Plastics additives, flavor and fragrances, and personal care products were reported by both LC-MS and GC-MS participants. It was concluded that the use of multiple analytical techniques was required for a comprehensive characterization of house dust contaminants. Further, several recommendations are given for improved suspect and nontarget screening of house dust and other indoor environment samples, including the use of open-source data processing tools. One of the tools allowed provisional identification of almost 500 compounds that had not been reported by participants.

  • 41.
    Sahlström, Leena
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sellström, Ulla
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Clean-up method for determination of established and emerging brominated flame retardants in dust2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 404, no 2, p. 459-466Article in journal (Refereed)
    Abstract [en]

    A clean-up method was developed to enable the determination of tri-decabrominated diphenyl ethers, isomer-specific hexabromocyclododecanes (HBCDs), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), decabromodiphenyl ethane (DBDPE), (2-ethylhexyl)tetrabromobenzoate (TBB), and bis(2-ethylhexyl)tetrabromophthalate (TBPH) in the same dust sample extract using reasonable amounts of solvents and without dividing the sample. After extraction, the sample was separated on a silica column into three fractions that were subsequently cleaned up individually. The polybrominated diphenyl ethers (PBDEs) and DBDPE were eluted in Fraction I, TBB, TBPH, and BTBPE in Fraction II, and HBCDs in Fraction III. Fractions I and II were analyzed using gas chromatography/mass spectrometry and Fraction III using liquid chromatography/mass spectrometry. The method gave good recoveries (60-120%), precise results using (13) C-labelled internal standards and was accurate when comparing results to certified values (PBDEs in NIST SRM 2585). The method was applied to dust samples from the Stockholm (Sweden) area. All the emerging brominated flame retardants (BFRs) studied, except BTBPE, were present in all the samples in quantifiable concentrations, often higher than the PBDEs. BTBPE was quantified in only one sample. It is evident that emerging BFRs are present in Swedish homes, and these compounds should be included in the BFR analyses of indoor environments.

  • 42.
    Shariatgorji, Mohammadreza
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Astorga-Wells, Juan
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Trends in the bioanalytical applications of microfluidic electrocapture2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, p. 191-195Article in journal (Refereed)
  • 43.
    Shariatgorji, Mohammadreza
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Astorga-Wells, Juan
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Trends in the bioanalytical applications of microfluidic electrocapture2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 1, p. 191-195Article in journal (Refereed)
    Abstract [en]

    Downscaled analytical tools for sample preparation have offered benefits such as higher throughput, easier automation and lower sample/reagent consumption. Microfluidic electrocapture, which is a newly developed sample preparation/manipulation system, uses an electric field to trap and separate charged species without using any solid sorbent. The feasibility of using microfluidic electrocapture is reported for separation, clean-up, concentration, microreactions and complexation studies of proteins, peptides and other biologically important biomolecules. The instrumentation and applications of microfluidic electrocapture are reviewed and an overview is provided of future perspectives offered by the current and envisaged platforms.

  • 44.
    Sousa, Pedro F. M.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    de Waard, Angela
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Elucidation of chromatographic peak shifts in complex samples using a chemometrical approach2018In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 410, no 21, p. 5229-5235Article in journal (Refereed)
    Abstract [en]

    Chromatographic retention time peak shifts between consecutive analyses is a well-known fact yet not fully understood. Algorithms have been developed to align peaks between runs, but with no specific studies considering the causes of peak shifts. Here, designed experiments reveal chromatographic shift patterns for a complex peptide mixture that are attributable to the temperature and pH of the mobile phase. These results demonstrate that peak shifts are highly structured and are to a high degree explained by underlying differences in physico-chemical parameters of the chromatographic system and also provide experimental support for the alignment algorithm called the generalized fuzzy Hough transform which exploits this fact. It can be expected that the development of alignment algorithms enters a new phase resulting in increasingly accurate alignment by considering the latent structure of the peak shifts.

  • 45.
    Tengstrand, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Rosén, Johan
    Hellenäs, Karl-Erik
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A concept study on non-targeted screening for chemical contaminants in food using liquid chromatography–mass spectrometry in combination with a metabolomics approach2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 4, p. 1237-1243Article in journal (Refereed)
    Abstract [en]

    A generic method to screen for new or unexpected contaminants at ppm levels in food has been developed. The method comprises an acidic acetonitrile extraction, detection with ultra-high-pressure liquid chromatography coupled to electrospray ionisation time-of-flight mass spectrometry and statistical evaluation using a metabolomics approach comparing suspected contaminated food with uncontaminated foods. The method was tested for 26 model contaminants from 100 μg/g down to 0.4 μg/g in three brands of fresh orange juice. Blinded statistical evaluation revealed signals from all added contaminants detectable by liquid chromatography –electrospray ionisation using positive ionisation mode, while only two false-positive signals were reported. The method is primarily intended to be used  for investigation of food samples suspected to be contaminated with unknown substances. Additionally it could be used to continuously monitor for appearance of new food contaminants as a complement to the specific targeted analysis that is today’s foundation of food safety analysis.

  • 46.
    Thewalim, Yasar
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Aldaeus, Fredrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Retention time prediction of compounds in Grob standard mixture for apolar capillary columns in temperature-programmed gas chromatography2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 393, no 1, p. 327-334Article in journal (Refereed)
    Abstract [en]

    This paper presents an extension of a previous investigation in which the behavior of nonpolar compounds in temperature-programmed gas chromatographic runs was predicted using thermodynamic (entropy and enthalpy) parameters derived from isothermal runs. In a similar manner, entropy and enthalpy parameters were determined for a Grob standard mixture of compounds with widely varying chemical characteristics. These parameters were used to predict the retention times and chromatographic behaviors of the compounds on four gas chromatography capillary columns: three that had phenyl-based stationary phases (with degrees of substitution of 0%, 5% and 50%) and one with (50%) cyanopropyl substitution. The predictions matched data empirically obtained from temperature-programmed chromatographic runs for all of the compounds extremely well, despite the wide variations in polarity of both the compounds and stationary phases. Thus, the results indicate that such simulations could greatly reduce the time and material costs of chromatographic optimizations.

  • 47.
    Thewalim, Yasar
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bruno, Oscar
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Study of the chromatographic behaviour of selected alcohols and amines2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 3, p. 1335-1345Article in journal (Refereed)
    Abstract [en]

    The gas chromatographic behavior of selected linear and non-linear alcohols and amines was investigated using four capillary columns containing phenyl substitution levels of 0%, 5%, and 50% and 50% cyanopropyl substitution. In a previous study, the positions of specific compounds inside the capillary column were iteratively modeled using only two thermodynamic parameters (ΔH and ΔS). The present study addresses the validation of the two-parameter model for retention time prediction for selected alcohols and amines using thermodynamic data obtained from as few as two data points. The difference between predicted and observed retention times under different temperature conditions was generally less than 1% of the experimental value and the predicted order of elution was correct in the used model.

  • 48.
    Tollbäck, Johanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Isetun, Sindra
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic non-equilibrium SPME combined with GC, PICI, and ion trap MS for determination of organophosphate esters in air2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 396, no 2, p. 839-844Article in journal (Refereed)
    Abstract [en]

    Methodology for time-weighted average (TWA) air measurements of semivolatile organophosphate triesters, widely used flame-retardants and plasticizers, and common indoor pollutants is presented. Dynamic non-equilibrium solid-phase microextraction (SPME) for air sampling, in combination with GC/PICI and ion trap tandem MS, yields a fast, almost solvent-free method with low detection limits. Methanol was used as reagent gas for PICI, yielding stable protonated molecules and few fragments. A field sampler, in which a pumped airflow over three polydimethylsiloxane (PDMS) 100-μm fibers in series was applied, was constructed, evaluated, and used for the measurements. The method LODs were in the range 2–26 ng m−3 for a sampling period of 2 h. The uptake on the SPME fibers was shown to be about five times faster for triphenyl phosphate compared to the other investigated organophosphate esters, most likely due to more lipophilic properties of the aromatic compound. The boundary layer for triphenyl phosphate when using a 100-µm PDMS sorbent was determined to 0.08 mm at a linear air velocity of 34 cm s−1. Five different organophosphate triesters were detected in air from a laboratory and a lecture hall, at concentrations ranging from 7 ng m−3 up to 2.8 μg m−3.

  • 49.
    Tran, Thi Thuy
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Inganas, Mats
    Thorsen, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    High-throughput profiling of N-linked oligosaccharides in therapeutic antibodies using a microfluidic CD platform and MALDI-MS2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 4, p. 1601-1611Article in journal (Refereed)
    Abstract [en]

    Recombinant therapeutic antibodies have shown a great potential in the treatment of several severe medical conditions such as cancer and autoimmune diseases. Glycosylation plays a critical role in biological activity and immunogenic properties of these compounds. The analysis of glycan profiles is therefore necessary in many steps of the development and manufacturing process from early development to quality control of the final product. In this paper, a fast, parallel, and robust sample preparation platform for glycosylation profiling using a microfluidic compact disc (CD) is presented. A sequential process including selective capture of antibody from a crude cell supernatant using protein A beads, enzymatic release of glycans, purification with a graphitized carbon black column, and crystallisation for MALDI-TOF analysis were performed on the CD. Glycosylation profiles of an antibody intended for therapeutic use produced in two different cell lines were compared.

  • 50.
    Ullah, Shahid
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Vestergren, Robin
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Berger, Urs
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Determination of perfluoroalkyl carboxylic, sulfonic, and phosphonic acids in food2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 404, no 8, p. 2193-2201Article in journal (Refereed)
    Abstract [en]

    A sensitive and accurate method was developed and validated for simultaneous analysis of perfluoroalkyl carboxylic acids, sulfonic acids, and phosphonic acids (PFPAs) at low picograms per gram concentrations in a variety of food matrices. The method employed extraction with acetonitrile/water and cleanup on a mixed-mode co-polymeric sorbent (C8 + quaternary amine) using solid-phase extraction. High-performance liquid chromatographic separation was achieved on a C18 column using a mobile phase gradient containing 5 mM 1-methyl piperidine for optimal chromatographic resolution of PFPAs. A quadrupole time-of-flight high-resolution mass spectrometer operating in negative ion mode was used as detector. Method detection limits were in the range of 0.002 to 0.02 ng g(-1) for all analytes. Sample preparation (extraction and cleanup) recoveries at a spiking level of 0.1 ng g(-1) to a baby food composite were in the range of 59 to 98 %. A strong matrix effect was observed in the analysis of PFPAs in food extracts, which was tentatively assigned to sorption of PFPAs to the injection vial in the solvent-based calibration standard. The method was successfully applied to a range of different food matrices including duplicate diet samples, vegetables, meat, and fish samples.

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