Change search
Refine search result
123456 1 - 50 of 279
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Abdel Rehim, Abbi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and determination of drugs in human saliva utilizing microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry2013In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 27, no 9, p. 1188-1191Article in journal (Refereed)
    Abstract [en]

    This study presents a new method for collecting and handling saliva samples using an automated analytical microsyringe and microextraction by packed syringe (MEPS). The screening and determination of lidocaine in human saliva samples utilizing MEPS and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were carried out. An exact volume of saliva could be collected. The MEPS C-8-cartridge could be used for 50 extractions before it was discarded. The extraction recovery was about 60%. The pharmacokinetic curve of lidocaine in saliva using MEPS-LC-MS/MS is reported.

  • 2. Abdel-Rehim, Abbi
    et al.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Advantages of Saliva Sampling in Bioanalysis Using Microextraction by Packed Sorbent and Dried Saliva Spot with LC-MS-MS2014In: LC GC Europe, ISSN 1471-6577, Vol. 27, no 10, p. 529-531Article in journal (Refereed)
    Abstract [en]

    Saliva offers a fast and non-invasive sampling matrix for determining drug concentration levels, making it a suitable alternative to plasma and blood. During the analysis of biological samples attention is focused on sample pre-treatment. In addition, liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) is often the method of choice in bioanalysis because of the good selectivity and good sensitivity of the technique. In this article, two sample handling and sample preparation methods for saliva samples are presented and discussed. The first method is microextraction by packed sorbent (MEPS), and the second method is dried saliva spot (DSS). Both methods were applied for determining the presence of lidocaine in saliva.

  • 3. Abdel-Rehim, Abbi
    et al.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dried saliva spot as a sampling technique for saliva samples2014In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 28, no 6, p. 875-877Article in journal (Refereed)
    Abstract [en]

    For the first time, dried saliva spot (DSS) was used as a sampling technique for saliva samples. In the DSS technique 50 L of saliva was collected on filter paper and the saliva was then extracted with an organic solvent. The local anesthetic lidocaine was used as a model compound, which was determined in the DSS using liquid chromatography and mass spectrometry. The results obtained for the determination of lidocaine in saliva using DSS were compared with those from a previous study using a microextraction by packed sorbent syringe as the sampling method for saliva. This study shows that DSS can be used for the analysis of saliva samples. The method is promising and very easy in terms of sampling and extraction procedures. The results from this study are in good agreement with those from our previous work on the determination of lidocaine in saliva. DSS can open a new dimension in the saliva handling process in terms of sampling, storing and transport.

  • 4.
    Abdel-Rehim, Abbi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of microextraction by packed sorbent and micro-liquid chromatography-tandem mass spectrometry as a green approach in bioanalysis2013In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 27, no 10, p. 1225-1233Article in journal (Refereed)
    Abstract [en]

    In this study the use of micro-liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was investigated in routine bioanalysis application for separation and quantification of pro-drug AZD6319 (developed for aldezheimer treatment). Microextraction by packed sorbent (MEPS) was used as sample clean-up method. The focus of this study was put on the evaluation of the usability of smaller column diameters such as 1.0 and 0.3mm instead of 2.1mm in bioanalysis application to reduce solvent consumption and sample volumes. Solvent consumption was reduced by 80% when a 1.0mm column was used compared with 2.1mm column. Robustness of the micro-columns in terms of accuracy and precision was investigated. The application of LC-MS/MS for the quantitative analysis of AZD6319 in plasma samples showed good selectivity, accuracy and precision. The coefficients of determination (R-2) were >0.998 for all runs using plasma samples on the studied micro-columns. The inter-day accuracy values for quality control samples ranged from 99 to 103% and from 96 to 105% for 0.3x50mm and 1.0x50mm columns, respectively. The inter-day precision values ranged from 4.0 to 9.0% and from 4.0 to 8.0% for 0.3x50 and 1.0x50mm columns, respectively. In addition the sensitivity was increased by three times using a 1.0mm column compared with 2.1mm. Furthermore, robustness of the micro-columns from different manufacturers was investigated.

  • 5.
    Ahmed, Trifa M.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Emissions of particulate associated oxygenated and native polycyclic aromatic hydrocarbons from vehicles powered by ethanol/gasoline fuel blendsManuscript (preprint) (Other academic)
  • 6.
    Aldaeus, Fredrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    New Tools for Trapping and Separation in Gas Chromatography and Dielectrophoresis: Improved Performance by Aid of Computer Simulation2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Computer simulations can be useful aids for both developing new analytical methods and enhancing the performance of existing techniques. This thesis is based on studies in which computer simulations were key elements in the development of several new tools for use in gas chromatography and dielectrophoresis. In gas chromatography, gaseous analytes are separated by exploiting differences in their partitioning between different phases, and after their partitioning parameters have been determined the separations can be computationally predicted, and optimized, for a wide range of operating conditions. Similarly, in dielectrophoresis, particles with differing polarizability or size can be separated, and since particle trajectories within a separation device can be predicted using computations, the suitability of new designs, applications of forces and combinations of operational parameters can be assessed without necessarily making or empirically testing all of the variants.

    Using two existing numerical methods combined with semi-empirical determinations of retention behavior, temperature-programmed gas chromatograms were predicted with less than one percent deviations from experimental data, and a new method for improving the capacity of a gas-trapping device was predicted and experimentally verified. In addition, two new concepts with potential capacity to enhance dielectrophoretic separations were developed and tested in simulations. The first provides a promising way to improve the trapping of bacteria in media with elevated conductivity by using super-positioned electric fields, and the second a way to increase selectivity in the separation of bio-particles by using multiple dielectrophoretic cycles. The studies also introduced a more accurate method for determining the conductivity of suspensions of bacteria, and a new computational method for determining the dielectrophoretic behavior of particles in concentrated suspensions.

    The scientific studies are summarized and discussed in the main text of this thesis, and presented in detail in seven appended papers.

  • 7.
    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 and peak widths in temperature-programmed gas chromatography using the finite element method2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 1, p. 134-139Article in journal (Refereed)
    Abstract [en]

    Optimization of separations in gas chromatography is often a time-consuming task. However, computer simulations of chromatographic experiments may greatly reduce the time required. In this study, the finite element method was used to predict the retention times and peak widths of three analytes eluting from each of four columns during chromatographic separations with two temperature programs. The data acquired were displayed in predicted chromatograms that were then compared to experimentally acquired chromatograms. The differences between the predicted and measured retention times were typically less than 0.1%, although the experimental peak widths were typically 10% larger than expected from the idealized calculations. Input data for the retention and peak dispersion calculations were obtained from isothermal experiments, and converted to thermodynamic parameters.

  • 8.
    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.

  • 9.
    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.

  • 10.
    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
    AstraZeneca R&D Sodertalje, Safety Assessment, Mol Toxicol, S-15185 Sodertalje, Sweden .
    Gustafsson, Ingela
    AstraZeneca R&D Sodertalje, Safety Assessment, Mol Toxicol, S-15185 Sodertalje, Sweden .
    Lindberg, Johan
    AstraZeneca R&D Sodertalje, Safety Assessment, Mol Toxicol, S-15185 Sodertalje, Sweden .
    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.

  • 11.
    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.

  • 12.
    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.

  • 13.
    Amelina, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjodin, Marcus O. D.
    Bergquist, Jonas
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC-MS/MS2011In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 879, no 30, p. 3393-3400Article in journal (Refereed)
    Abstract [en]

    Aging is a complex multifactorial phenomenon, which is believed to result from the accumulation of cellular damage to biological macromolecules. Peroxisomes recently emerged as another important source of reactive oxygen species (ROS) production in addition to mitochondria. However, the role of these organelles in the process of aging is still not clear. The aim of this study was to characterize the changes in protein expression profiles of young (10 weeks old) versus old (18 months old) mouse liver peroxisome-enriched fractions. We have applied shotgun proteomic approach based on liquid chromatography and tandem mass spectrometry (LC-MS/MS) combined with iTRAQ (isobaric tags for relative and absolute quantitation) labeling that allows comparative quantitative multiplex analysis. Our analysis led to identification and quantification of 150 proteins, 8 out of which were differentially expressed between two age groups at a statistically significant level (p < 0.05), with folds ranging from 1.2 to 4.1. These proteins involved in peroxisornal beta-oxidation, detoxification of xenobiotics and production of ROS. Noteworthy, differences in liver proteome have been observed between as well as within different age groups. In conclusion, our subproteomic quantitative study suggests that mouse liver proteome is sufficiently maintained until certain age.

  • 14.
    Amelina, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjödin, Marcus O. D.
    Bergquist, Jonas
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC-MS/MSIn: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376XArticle in journal (Refereed)
  • 15.
    Amini, Nahid
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Novel Solid Phase Extraction and Mass Spectrometry Approaches to Multicomponent Analyses in Complex Matrices2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Analysis of compounds present in complex matrices is always a challenge, which can be partly overcome by applying various sample preparation techniques prior to detection. Ideally, the extraction techniques should be as selective as possible, to minimize the concentration of interfering substances. In addition, results can be improved by efficient chromatographic separation of the sample components. The elimination of interfering substances is especially important when utilizing mass spectrometry (MS) as a detection technique since they influence the ionization yields. It is also important to optimize ionization methods in order to minimize detection limits.

    In the work this thesis is based upon, selective solid phase extraction (SPE) materials, a restricted access material (RAM) and graphitized carbon black (GCB) were employed for clean up and/or pre-concentration of analytes in plasma, urine and agricultural drainage water prior to liquid chromatography/mass spectrometry (LC/MS). Two SPE formats, in which GCB was incorporated in µ-traps and disks, were developed for cleaning up small and large volume samples, respectively. In addition, techniques based on use of sub-2 µm C18 particles at elevated temperatures and a linear ion trap (LIT) mass spectrometer were developed to improve the efficiency of LC separation and sensitivity of detection of 6-formylindolo[3,2-b]carbazole (FICZ) metabolites in human urine.

    It was also found that GCB can serve not only as a SPE sorbent, but also as a valuable surface for surface-assisted laser desorption ionization (SALDI) of small molecules. The dual functionality of GCB was utilized in a combined screening-identification/quantification procedure for fast elimination of negative samples. This may be particularly useful when processing large numbers of samples. SALDI analyses of small molecules was further investigated and improved by employing two kinds of new surfaces: oxidized GCB nanoparticles and silicon nitride.

  • 16.
    Amini, Nahid
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thorsen, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and Quantification of Pesticides in Water Using a Dual-Function Graphitized Carbon Black Disk (Addition/Correction)2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, p. 631-631Article in journal (Refereed)
  • 17.
    Amini, Nahid
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Thorsén, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and Quantification of Pesticides in Water Using a Dual-Function Graphitized Carbon Black Disk2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 1, p. 290-296Article in journal (Refereed)
    Abstract [en]

    A simple platform for combining solid phase extraction (SPE) and surface-assisted laser desorption ionization mass spectrometry (SALDI-MS) of extracted analytes, using disks prepared by embedding graphitized carbon black (GCB-4) particles in a network of polytetrafluoroethylene (PTFE), is presented. The system provides a convenient approach for rapid SALDI-MS screening of substances in aqueous samples, which can be followed by robust quantitative and/or structural analyses by liquid chromatography (LC)/MS/MS of positive samples. The extraction discs are easily transferred between gaskets where the sample extraction and desorption of selected samples is performed and the mass spectrometer. The SPE and SALDI properties of the new GCB-4 disc have been characterized for 15 pesticides with varying chemical properties, and the screening strategy has been applied to the analysis of pesticides in agricultural drainage water. Atrazine and atrazine-desethyl-2-hydroxy were detected in the sampled water by SALDI-MS screening and subsequently confirmed and quantified using LC/MS/MS.

  • 18. Aminlashgari, Nina
    et al.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hakkarainen, Minna
    Nanocomposites as novel surfaces for laser desorption ionization mass spectrometry2011In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 3, no 1, p. 192-197Article in journal (Refereed)
    Abstract [en]

    The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.

  • 19.
    Andersson, Magnus B. O.
    Stockholm University.
    Development of new techniques for micro-packed high performance liquid chromatography and supercritical fluid methods2000Doctoral thesis, comprehensive summary (Other academic)
  • 20. Andersson, P
    et al.
    Jesson, G
    Kylberg, G
    Ekstrand, G
    Thorsén, G
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Parallel nanoliter microfluidic analysis system2007In: Anal Chem, Vol. 79, p. 4022-4030Article in journal (Refereed)
  • 21.
    Andersson, Per
    Stockholm University, Faculty of Science.
    Separation and detection techniques in capillary electrophoresis1995Doctoral thesis, comprehensive summary (Other academic)
  • 22.
    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.

  • 23.
    Avagyan, Rozanna
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    From source to the environment: Strategies for identification and determination of hydroxylated polycyclic aromatic hydrocarbons in complex particulate matrices2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Adverse health effects have been linked to exposure to particulate matter, and wood combustion is considered as an important source of harmful particulate matter in the urban air and environment. Hydroxylated polycyclic aromatic hydrocarbons are a group of compounds with toxic, endocrine disrupting and carcinogenic properties. Sources of hydroxylated polycyclic aromatic hydrocarbons are different incomplete combustion processes, such as coal and wood combustion. They can also be formed by microbiological and/or photochemical degradation of polycyclic aromatic hydrocarbons in the environment.

    This thesis describes analytical strategies and methods that have been developed and used for screening, tentative identification and determination of hydroxylated polycyclic aromatic hydrocarbons in wood combustion and urban air particles. Conventional targeted analytical methods have been developed for compounds with available reference standards, while suspect and non-target screening strategies have been used for the identification of suspects and unknown compounds lacking reference standards. Each step of the developed analytical methods is described and discussed: the choice of the analytical strategy, sampling of the matrices, extraction, clean-up, instrumental analysis, data processing and validation of the methods.

    The influence of wood type (birch, spruce, pine and aspen) and burning conditions (nominal and high burn rate) on the hydroxylated polycyclic aromatic hydrocarbon emissions has been examined, showing that emissions from nominal burn rate combustion correspond on average to 14 % of the emissions from high burn rate combustion. It has been shown that spruce and pine have the highest emissions for nominal burn rate and high burn rate combustion, respectively.

    The composition of wood combustion particles has been examined and 32 suspect hydroxylated polycyclic aromatic hydrocarbons have been tentatively identified together with 20 other oxygen-containing small molecular weight compounds. Furthermore, the presence of hydroxylated polycyclic aromatic hydrocarbons in airborne particles from an urban background and a car tunnel has been investigated, and nine target and 11 suspect hydroxylated polycyclic aromatic hydrocarbons have been determined and tentatively identified, respectively.

    In summary, this thesis has shown that wood combustion is an important emission source of hydroxylated aromatic hydrocarbons and that the chemical composition of the emitted particles strongly depends on both burning conditions and wood type. Furthermore, the findings suggest that there might be other sources of these compounds in the urban environment than wood burning, such as the traffic. Thus, further investigations are required to fully understand the formation, sources and presence of hydroxylated polycyclic aromatic hydrocarbons in the atmosphere. The suitability of different analytical strategies and methods for identification and determination of hydroxylated polycyclic aromatic hydrocarbons is also discussed.

  • 24.
    Avagyan, Rozanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sadiktsis, Ioannis
    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.
    Tire tread wear particles in ambient air—a previously unknown source of human exposure to the biocide 2-mercaptobenzothiazole2014In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 21, no 19, p. 11580-11586Article in journal (Refereed)
    Abstract [en]

    Urban particulate matter (PM), asphalt, and tire samples were investigated for their content of benzothiazole and benzothiazole derivates. The purpose of this study was to examine whether wear particles, i.e., tire tread wear or road surface wear, could contribute to atmospheric concentrations of benzothiazole derivatives. Airborne particulate matter (PM10) sampled at a busy street in Stockholm, Sweden, contained on average 17 pg/m3 benzothiazole and 64 pg/m3 2-mercaptobenzothiazole, and the total suspended particulate-associated benzothiazole and 2-mercaptobenzothiazole concentrations were 199 and 591 pg/m3, respectively. This indicates that tire tread wear may be a major source of these benzothiazoles to urban air PM in Stockholm. Furthermore, 2-mercaptobenzothiazole was determined in urban air particulates for the first time in this study, and its presence in inhalable PM10 implies that the human exposure to this biocide is underestimated. This calls for a revision of the risk assessments of 2-mercaptobenzothiazole exposure to humans which currently is limited to occupational exposure.

  • 25.
    Avagyan, Rozanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thorsen, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of benzothiazole and benzotriazole derivates in tire and clothing textile samples by high performance liquid chromatography-electrospray ionization tandem mass spectrometry2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1307, p. 119-125Article in journal (Refereed)
    Abstract [en]

    A high performance liquid chromatography–tandem mass spectrometry method utilizing electrospray ionization in positive and negative mode has been developed for the separation and detection of benzothiazole and benzotriazole derivates. Ultra-sonication assisted solvent extraction of these compounds has also been developed and the overall method demonstrated on a selected clothing textile and an automobile tire sample. Matrix effects and extraction recoveries, as well as linearity and limits of detection have been evaluated. The calibration curves spanned over more than two orders of magnitude with coefficients of correlation R2 > 0.99 and the limits of detection and the limits of quantification were in the range 1.7–58 pg injected and 18–140 pg/g, respectively. The extraction recoveries ranged between 69% and 102% and the matrix effects between 75% and 101%. Benzothiazole and benzotriazole derivates were determined in the textile sample and benzothiazole derivatives determined in the tire sample with good analytical performance.

  • 26.
    Axelsson, Sara
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Resin acids in commercial products and the work environment of Swedish wood pellets production: Analytical methodology, occurrence and exposure2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aims of the work this thesis is based upon were to develop convenient analytical procedures for determining resin acids in biological and environmental matrices, and apply them to enhance understanding of the occurrence, exposure to and uptake by exposed individuals of resin acids. Particular focus has been on the workplace environment of the Swedish wood pellets industry. Sample extraction procedures and high-performance liquid chromatography/electrospray ionisation-mass spectrometry (HPLC/ESI-MS) methodologies were developed for measuring resin acids in dust, skin and urine samples. Chromatographic separation of abietic (AA) and pimaric acid was achieved by using a polar-embedded C12 stationary phase. The HPLC/ESI-MS method avoids undesirable oxidation of AA, which was found to occur during the derivatisation step in the standard MDHS 83/2 gas chromatography/flame ionisation detection (GC/FID) methodology, leading to false observations of both AA and the oxidation product 7-oxodehydroabietic acid (7-OXO). Personal exposures to resin acids in the Swedish wood pellet production industry were found to be lower, on average, than the British Occupational Exposure Limit for rosin (50 µg/m3). The oxidised resin acid 7-OXO, was detected in both dust and skin samples indicating the presence of allergenic resin acids. A correlation between air and post-shift urinary concentrations of dehydroabietic acid (DHAA), and a trend towards an increase in urinary 7-OXO during work shifts, were also observed. Whether the increase in 7-OXO was due to direct uptake or metabolism of other resin acids cannot be concluded from the results. An efficient HPLC/UV methodology with diode-array detection was developed for screening commercial products for rosin that could be used in laboratories lacking mass spectrometers. Very high concentrations of free resin acids were detected in depilatory wax strips using the method.

  • 27.
    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)
  • 28.
    Baldassarre, Maurizio
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Pushing the detection limit of infrared spectroscopy for structural analysis of dilute protein samples.2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 21, p. 5393-5399Article in journal (Refereed)
    Abstract [en]

    Fourier-transform infrared spectroscopy is a powerful and versatile tool to investigate the structure and dynamics of proteins in solution. The intrinsically low extinction coefficient of the amide I mode, the main structure-related oscillator, together with the high infrared absorptivity of aqueous media, requires that proteins are studied at high concentrations (>10 mg L(-1)). This may represent a challenge in the study of aggregation-prone proteins and peptides, and questions the significance of structural data obtained for proteins physiologically existing at much lower concentrations. Here we describe the development of a simple experimental approach that increases the detection limit of protein structure analysis by infrared spectroscopy. Our approach relies on custom-made filters to isolate the amide I region (1700-1600 cm(-1)) from irrelevant spectral regions. The sensitivity of the instrument is then increased by background attenuation, an approach consisting in the use of a neutral density filter, such as a non-scattering metal grid, to attentuate the intensity of the background spectrum. When the filters and grid are combined, a 2.4-fold improvement in the noise level can be obtained. We have successfully tested this approach using a highly diluted solution of pyruvate kinase in deuterated medium (0.2% w/v), and found that it provides spectra of a quality comparable to those recorded with a 10-fold higher protein concentration.

  • 29.
    Baldassarre, Maurizio
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    The carbonate/bicarbonate system as a pH indicator for infrared spectroscopy2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 9, p. 2167-2176Article in journal (Refereed)
    Abstract [en]

    Caged compounds capable of inducing large pH-jumps upon UV illumination have represented a breakthrough in time-resolved infrared spectroscopy of acidification-triggered phenomena, but their use is hampered by the inability to control the initial pH as well as to measure the final pH in mu L volumes. We have developed an experimental approach that accurately measures the initial and final pH values in pH-jump experiments. Our approach exploits the concomitant presence of two or more inorganic ions, such as carbonate and bicarbonate, that are added to the sample at a known concentration. The difference spectrum obtained in the infrared measurement is fitted to isolate the bands arising from the appearance or disappearance of either protonation state, and is then compared to a synthetic library of difference spectra generated using both qualitative (band position and width, extinction coefficient, pK) and quantitative (concentration, pathlength) parameters of the reporter ions. We have tested this approach in UV-photolysis experiments of 1-(2-nitrophenyl)ethyl sulfate in the presence of different concentrations of Na2CO3 and successfully used the infrared absorption of the carbonate and the bicarbonate ions to determine the initial and final pH values before and after the pH-jump, respectively.

  • 30.
    Baldassarre, Maurizio
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Bennett, Matthew
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Simultaneous acquisition of infrared, fluorescence and light scattering spectra of proteins: direct evidence for pre-fibrillar species in amyloid fibril formation2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 3, p. 963-973Article in journal (Refereed)
    Abstract [en]

    Different spectroscopic approaches are often used to probe specific aspects of amyloid fibril formation but are usually performed separately and under different conditions. This makes it problematic to relate different aspects of the aggregation process when these are monitored by different methods. We report on a multispectral approach for simultaneous acquisition of infrared, fluorescence and light scattering spectra of proteins undergoing aggregation. We have applied our approach to study beta-lactoglobulin, a milk protein known to form amyloid fibrils under well-established conditions. Our real-time multispectral measurements show that unfolding of this protein is followed by formation of early aggregates consisting of intermolecular beta-sheets with a typical infrared absorption at similar to 1619 cm(-1) in (H2O)-H-2. These aggregates, which lead to an increase in the light scattering signal, do not bind the amyloid-specific fluorophore ThT and therefore consist of oligomers or protofibrils. Fibril growth is then observed as a sigmoidal increase in ThT fluorescence. After similar to 25 h, a plateau is observed in the intensities of ThT emission and of the band at 1619 cm(-1), indicating that no new fibrils are forming. However, a second phase in the light scattering signal taking place after similar to 25 h suggests that the fibrils are assembling into larger structures, known as mature fibrils. This is associated with an upshift of the main beta-sheet band in the infrared spectrum. TEM analyses confirmed the existence of thick fibrils comprising 3-5 filaments.

  • 31. Banack, Sandra Anne
    et al.
    Metcalf, James S.
    Jiang, Liying
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Craighead, Derek
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Cox, Paul Alan
    Cyanobacteria Produce N-(2-Aminoethyl)Glycine, a Backbone for Peptide Nucleic Acids Which May Have Been the First Genetic Molecules for Life on Earth2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 11, p. e49043-Article in journal (Refereed)
    Abstract [en]

    Prior to the evolution of DNA-based organisms on earth over 3.5 billion years ago it is hypothesized that RNA was the primary genetic molecule. Before RNA-based organisms arose, peptide nucleic acids may have been used to transmit genetic information by the earliest forms of life on earth. We discovered that cyanobacteria produce N-(2-aminoethyl)glycine (AEG), a backbone for peptide nucleic acids. We detected AEG in axenic strains of cyanobacteria with an average concentration of 1 µg/g. We also detected AEG in environmental samples of cyanobacteria as both a free or weakly bound molecule and a tightly bound form released by acid hydrolysis, at concentrations ranging from not detected to 34 µg/g. The production of AEG by diverse taxa of cyanobacteria suggests that AEG may be a primitive feature which arose early in the evolution of life on earth

  • 32. Bassyouni, Fatma
    et al.
    ElHalwany, Noha
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Munir, Neyfeh
    Advances and new technologies applied in controlled drug delivery system2015In: Research on chemical intermediates (Print), ISSN 0922-6168, E-ISSN 1568-5675, Vol. 41, no 4, p. 2165-2200Article in journal (Refereed)
    Abstract [en]

    A drug delivery system is defined as a formulation or a device that enables the introduction of a therapeutic substance into the body and improves its efficacy and safety by controlling the rate, time, and place of release of drugs in the body. This process includes the administration of the therapeutic product, the release of the active ingredients by the product, and the subsequent transport of the active ingredients across the biological membranes to the site of action. Drug delivery systems aim to improve patient compliance and convenience, such as, for example, fast-dissolving tablets. One of the most important goals of pharmaceutical science is localizing the pharmacological activity of the drug at the site of action. Drug delivery systems are molecular tools which, without undesired interactions at other sites, target a specific drug receptor. Keeping in view the advantages of the delivery system, rapidly disintegrating dosage forms have been successfully commercialized, and, because of increased patient demand, these dosage forms are expected to become more popular. Modern drug delivery technology has been made possible by advances in polymer science. These advances have resulted in polymers with unique properties. Drug delivery systems are made from a variety of organic and inorganic compounds such as polymers, lipids (liposomes, nanoemulsions, and solid-lipid nanoparticles), self-assembling amphiphilic molecules, dendrimers, and inorganic nanocrystals. In addition, hydrogels are novel delivery systems that have attracted much attention in current pharmaceutical research.

  • 33.
    Bergh, Caroline
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Organophosphates and phthalates in air and dust from indoor environments: Method development and applied measurements2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Organophosphate and phthalate esters are polymer additives that are frequently found in air and dust in indoor environments. This thesis describes the development and application of air sampling and selective mass spectrometric (MS) determination of these two compound groups. It also describes the sampling and screening of these compounds in indoor air and dust from different environments and the development and evaluation of a method for the extraction and determination of these compounds in indoor dust.

    An air sampling method previously used for air sampling of only organophosphate esters, is here demonstrated to be applicable for simultaneous sampling of both phthalate and organophosphate esters. Selective detection using tandem mass spectrometry (MS/MS) showed good results for simultaneous determination of organophosphate and phthalate esters in air. The high selectivity of this technique was especially advantageous when analyzing dust.

    Comparison of chemical profiles of the organophosphate ester between indoor environments including daycare centers, offices and private homes differed between the types of locations while the phthalate profiles were rather similar. Comparison of concentration levels of these compounds in multi-storey apartment buildings classified as either high or low risk “sick” buildings could not differentiate the two classes of buildings. Further, the studies also points out some potential sources of organophosphate and phthalate esters in these indoor environments.

    In general the levels of phthalate esters were consistently higher than the levels of organophosphate esters both in air and in dust. Phthalate and organophosphate esters were also determined in a dust standard reference material; seventeen of the targeted compounds were quantified out of which ten had not previously been reported for this reference material.

  • 34.
    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.

  • 35.
    Bergh, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Emenius, G.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Organophosphate and phthalate esters in air and settled dust – a multi-location indoor study2011In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 21, no 1, p. 67-76Article in journal (Refereed)
    Abstract [en]

    This paper reports the abundance in indoor air and dust of eleven organophosphate esters and six phthalate esters. Both groups of these semi-volatile compounds are widely incorporated as additives into plastic materials used in the indoor environment, thus contributing to indoor exposure to industrial chemicals. Thirty sampling sites representing three different indoor environments (private homes, day care centers, and workplaces) in the Stockholm area, Sweden, were selected to obtain representative concentration profiles in both ambient air and settled dust. Eight of the target organophosphate esters and all six phthalate esters were found in both air and dust samples at all locations. The phthalate esters were more abundant than the organophosphate esters, typically ten times higher total concentrations. Especially interesting were the high levels of tributoxyethyl phosphate in the day care centers, the relatively high levels of chlorinated organophosphate esters in the air of workplaces and the overall high levels of diethylhexyl phthalate in dust. The air concentration profiles of the phosphate esters differed significantly between the three indoor environments, whereas the concentration profiles of the phthalate esters as well as their total concentrations were similar. The correlation between concentrations found in air and in dust was found to be weak.

  • 36.
    Bergh, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Simultaneous selective detection of organophosphate and phthalate esters using gas chromatography with positive ion chemical ionization tandem mass spectrometry and its application to indoor air and dust2010In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 24, no 19, p. 2859-2867Article in journal (Refereed)
    Abstract [en]

    A selective and sensitive method for the simultaneous determination of 14 organophosphate and six phthalate esters using gas chromatography (GC) and mass spectrometry (MS) is presented. Both of these compound classes are frequently found in the indoor environment due to their use as bulk additives in numerous polymers, consumer products and building materials. GC/MS utilizing positive ion chemical ionisation (PICI) in selected reaction monitoring (SRM) mode with isobutane as the reagent gas was found to be the best of the tested methods; it proved superior to electron ionisation (EI) in selected ion monitoring (SIM) mode and to PICI using methane as the reagent gas. The method was applied to indoor air samples collected by active air sampling using solid-phase extraction (SPE) cartridges. Organophosphates and phthalates were simultaneously determined with method detection limits (MDLs) in the range of 0.1-47 ng m(-3). For most compounds the MDLs were <= 0.2 ng m(-3), but due to the presence of some of these ubiquitous indoor air pollutants in the blanks, significantly higher MDLs were observed for a few compounds. Finally, the method was also applied in the screening of a much more complex sample matrix, indoor dust.

  • 37.
    Bergh, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Svartengren, Magnus
    Emenius, Gunnel
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Organophosphate and phthalate esters in indoor air: a comparison between multi-storey buildings with high and low prevalence of sick building symptoms2011In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 13, no 7, p. 2001-2009Article in journal (Refereed)
    Abstract [en]

    An extensive study has been conducted of the prevalence of organophosphorous flame retardants/plasticizers and phthalate ester plasticizers in indoor air. The targeted substances were measured in 45 multi-storey apartment buildings in Stockholm, Sweden. The apartment buildings were classified as high or low risk with regard to the reporting of sick building symptoms (SBS) within the project Healthy Sustainable Houses in Stockholm (3H). Air samples were taken from two to four apartments per building (in total 169 apartments) to facilitate comparison within and between buildings. Association with building characteristics have been examined as well as association with specific sources by combining chemical analysis and exploratory uni- and multivariate data analysis. The study contributes to the overall perspective of levels of organophosphate and phthalate ester in indoor air enabling comparison with other studies. The results indicated little or no difference in the concentrations of the target substances between the two risk classifications of the buildings. The differences between the apartments sampled within (inter) buildings were greater than the differences between (intra) buildings. The concentrations measured in air ranged up to 1,200 ng/m3 for organophosphate esters and up to 11,000 ng/m3 for phthalate esters. Results in terms of sources were discerned e.g. PVC flooring is a major source of benzylbutyl phthalate in indoor air.    

  • 38.
    Bergqvist, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Methods for the characterization of triacylglycerol and glycoglycerolipid molecular species1995Doctoral thesis, comprehensive summary (Other academic)
  • 39.
    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.

  • 40.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Methods for Determination of Benzo(a)pyrene and High Molecular Weight (>300 Da) Polycyclic Aromatic Hydrocarbons in Particulate Matter from Ambient Air and Vehicle Exhausts2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Air pollution with particulate matter (PM) raises considerable concern because of its adverse effects on human health. For this reason, and because the mechanisms of PM toxicity are not fully known, there is an urgent need to determine the chemical constituents of atmospheric PM, especially PM emanating from traffic - a major source of urban PM.

    This thesis describes analytical methods that have been developed for determining polycyclic aromatic hydrocarbons (PAHs) in ambient air and vehicle exhaust PM, focusing particularly on benzo(a)pyrene (B(a)P) and the dibenzopyrenes: dibenzo(a,l)pyrene, dibenzo(a,e)pyrene, dibenzo(a,i)pyrene and dibenzo(a,h)pyrene. Trace amounts in complex matrices have been met by coupling parts or the entire clean-up step using liquid chromatography on-line with the analysis step using gas chromatography-mass spectrometry into one automated system.

    Application of the methodology, using either ultrasonic assisted extraction (USE) or accelerated solvent extraction (ASE), to a National Institute of Standards and Technology (NIST) urban air standard reference material (SRM) yielded comparable or higher concentrations than the assigned NIST values, validating the approach. However, ASE provided higher extraction yields from diesel particulate SRMs than USE, and ASE of diesel SRMs generally yielded higher concentrations than the corresponding NIST values.

    Concentrations of dibenzopyrenes in Stockholm air PM, and gasoline- and diesel-fuelled vehicle emissions (ng/km), are reported for the first time. When adjusted in terms of their relative carcinogenic potencies, the dibenzopyrenes were found to pose greater carcinogenic hazards than B(a)P, indicating that the current use of B(a)P as a marker probably leads to underestimates of the carcinogenicity of PAHs in ambient air.

    The developed methods also worked well for analyzing larger molecular weight PAHs: more than 60 and 170 potential PAHs were detected in ambient air PM and diesel PM, respectively.

  • 41.
    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 highly carcinogenic dibenzopyrene isomers in particulate emissions from two diesel- and two gasoline-fuelled light-duty vehicles2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 25, p. 3883-3890Article in journal (Refereed)
    Abstract [en]

    Emission factors of particulate-bound Polycyclic Aromatic Hydrocarbons (PAHs) including benzo(a)pyrene and, for the first time, the highly carcinogenic dibenzo(a,l)pyrene, dibenzo(a,e)pyrene, dibenzo(a,i)pyrene and dibenzo(a,h)pyrene have been determined in exhausts from two diesel- (DFVs) and two gasoline-fuelled light-duty vehicles (GFVs) operated in the Urban (AU), Rural Road (AR) and Motorway (AM) transient ARTEMIS driving cycles. The obtained results showed the DFVs to emit higher amounts of PAHs than the GFVs per km driving distance at low average speed in the AU driving cycle, while the GFVs emitted higher amounts of PAHs than the DFVs per km driving distance at higher average speeds in the AR and AM driving cycles. Furthermore, the study showed an increase in PAH emissions per km driving distance with increasing average speed for the GFVs with the opposite trend found for the DFVs. The GFVs generated particulate matter with higher PAH content than the DFVs in all three driving cycles tested with the highest concentrations obtained in the AR driving cycle. Dibenzo(a,l)pyrene was found to be a major contributor to the potential carcinogenicity accounting for 58–67% and 25–31% of the sum added potential carcinogenicity of the measured PAHs in the emitted particulate matter from the DFVs and GFVs, respectively. Corresponding values for benzo(a)pyrene were 16–25% and 11–40% for the DFVs and GFVs, respectively. The DFVs displayed higher sum added potential carcinogenicity of the measured PAHs than the GFVs in the AU driving cycle with the opposite trend found in the AR and AM driving cycles. The findings of this study show the importance of including the dibenzopyrenes in vehicle exhaust chemical characterizations to avoid potential underestimation of the carcinogenic activity of the emissions. The lower emissions and the lower sum added potential carcinogenicity of the measured PAHs found in this study for the GFVs compared to the DFVs in the AU driving cycle indicate the GFVs to be preferred in dense urban areas with traffic moving at low average speeds with multiple start and stops. However, the obtained results suggest the opposite to be true at higher average speeds with driving at rural roads and motorways. Further studies are, however, needed to establish if the observed differences between GFVs and DFVs are generally valid as well as to study the effects on variations in vehicle/engine type, ambient temperature, fuel and driving conditions on the emission factors.

  • 42.
    Bergvall, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Identification and Determination of Highly Carcinogenic Dibenzopyrene Isomers in Air Particulate Samples from a Street Canyon, a Rooftop, and a Subway Station in Stockholm2007In: Environmental Science & Technology, ISSN 0013-936X, Vol. 41, no 3, p. 731-737Article in journal (Refereed)
    Abstract [en]

    This study presents determined levels of the highly carcinogenic dibenzopyrene isomers dibenzo(a,l)pyrene, dibenzo(a,e)pyrene, dibenzo(a,i)pyrene, and dibenzo(a,h)pyrene as well as three other polycyclic aromatic hydrocarbons (PAHs)benzo(a)pyrene, perylene and coronenein ambient particulate material samples from a street canyon, a rooftop, and an underground subway station in Stockholm, Sweden. To our knowledge, these are the first reported determinations of dibenzopyrene isomers in air particles from either Stockholm or a subway station. Taking into account both concentration and toxic equivalence factors (TEFs), the PAH with the highest carcinogenic potency in the analyzed samples was dibenzo(a,l)pyrene, and the sum carcinogenic potency of the determined dibenzopyrenes was about 1−4 times higher than that of benzo(a)pyrene in the analyzed samples. These findings indicate that it is important to analyze the dibenzopyrene isomers as well as benzo(a)pyrene; the common approach of using benzo(a)pyrene as an indicator substance could lead to underestimates of the potential carcinogenic potency of PAHs in ambient air. The results also indicate that the relative carcinogenic potency of the determined dibenzopyrenes and benzo(a)pyrene in air particles from Stockholm is similar to that of air particles sampled in Washington in 1976−1977, despite general improvements in air quality in the intervening period. However, more data are needed to characterize temporal variations in dibenzopyrene levels in locations such as subway stations, suburbs, road tunnels, and metropolitan areas. There is also a need to identify and characterize both stationary and mobile PAH sources with respect to emission of dibenzopyrene isomers.

  • 43. Bjurshammar, N
    et al.
    Buhlin, K
    Tranæus, S
    Johannsen, A
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    On the Red Fluorescence Emission of Aggregatibacter actinomycetemcomitans2012In: Open Journal of Stomatology, ISSN 2160-8709, no 2, p. 299-306Article in journal (Refereed)
    Abstract [en]

    A number of studies have indicated that bacteria able to emit red fluorescence can be detected by light in-duced fluorescence technique and killed by photody-namic therapy. The objective of this study was to in-vestigate the red fluorescence properties of the single gram negative capnophilic bacterium Aggregatibacter actinomycetemcomitans, ATCC 33384, and to investi-gate if these properties were related to the growth, morphology and size of the bacterial colonies. Time trend assessment was made with red fluorescence by QLF (Quantitative Light-induced Fluorescence), as well as with white light digital imaging. It was dem-onstrated that A. actinomycetemcomitans, a single cap-nophilic bacterium, is able to produce red fluores-cence on its own, i.e. in the absence of other bacteria strains, and that blood agar is necessary to obtain red fluorescence from this bacterium on culture plates. This bacterium formed smooth circular, bell/dome like colonies increasing in size with time exhibiting various red fluorescence behaviors. A large variation in the fluorescence behavior points out an inhomoge-neous distribution of red fluorescence within and be-tween the colonies, i.e. the size of the investigated colonies did not correlate with the red fluorescence area, suggesting a dependence on the colony mor-phology such as the colony growth in height. To our knowledge this is the first study that have shown that A. actinomycetemcomitans on its own is able to pro-duce fluorescence in the red spectral region.

  • 44. Bjurshammar, N.
    et al.
    Malmqvist, S.
    Johannsen, G.
    Boström, E. A.
    Fyrestam, Jonas
    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.
    Johannsen, A.
    The Effect of Local Phototherapy on Gingival Inflammation - A Randomized Controlled StudyManuscript (preprint) (Other academic)
    Abstract [en]

    Aim: To investigate if a toothbrush with incorporated 450 nm LEDs used in daily oral care can reduce dental plaque and gingival inflammation.

    Materials and methods: An 8-week single blinded randomized clinical trial comparing toothbrushes with and without 450 nm blue LED light emission including 48 subjects. Clinical parameters of interest were plaque index (PI), gingival index (GI) and bleeding on probing (BOP). Analyzes were also made on Interleukin-1β (IL), IL-6, IL -8, and Tumor necrosis factor alpha.

    Results: A significant reduction in PI, GI and BOP was detected within the groups from baseline to follow-up visit, but no statistical differences between subjects using a toothbrush with 450 nm blue light and a toothbrush without light. Significant decreases in the levels of both MMP-8 and TIMP-1 in saliva, and IL-1b and IL-8 in GCF for the blue light toothbrush groups.

    Conclusion: A toothbrush with 450 nm LEDs did not yield any statistical significant adjunctive effect to tooth brushing with regard to reduction in gingival inflammation. A larger decrease in PI for the blue light toothbrush compared to control was found at a significance level of p=0.058. To get an optimal phototherapeutic effect we suggest that a wavelength of 405 nm should be used in future studies.

  • 45.
    Björklund, Jonas
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Gas chromatography and mass spectrometry of polybrominated diphenyl ethers2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [sv]

    The aim of this thesis has been to develop accurate and sensitive analytical methods for the determination of polybrominated diphenyl ethers (PBDEs). It focuses on the development and optimization of gas chromatographic and mass spectrometric analysis of PBDE.

    PBDEs are widely used as additative flame retardants and an increasing environmental occurrence and persistence rise concern about these compounds as environmental contaminants. However, the chemical and physical properties of the PBDEs yield a number of problems associated with the analysis of these compounds. This thesis provides an overview of the gas chromatographic separation system used for determination of PBDE and suggestions of improvements of the analytical methods. It is shown that by careful selection and optimization of the injection technique, the column system and the detection technique, the precision of the analytical method for PBDEs is significantly improved.

    To increase sensitivity and overcome some of the problems associated with sample preparation, large volume injection technique is recommended. Both large volume programmable temperature vaporizing (PTV) injection and the loop type injector has been optimized and evaluated with respect to the PBDEs. It is also demonstrated that the GC injection technique most commonly used for PBDE analysis, discriminate the high molecular weight congeners such as the decabrominated diphenyl ether congener (BDE-209).

    The dimensions and the type of GC column system strongly affect the yield of the PBDE. Degradation in the GC system of high molecular weight polybrominated diphenyl ether (BDE) congeners, especially BDE-209, is also dependent on the residence time in the column system. There is a large difference in performance between columns with supposedly similar stationary phase and by selecting a short narrow bore columns it is possible to dramatically decrease the degradation of high molecular weight PBDEs.

    Mass spectrometric properties of BDE-209 is presented, and carbon 13 labeled BDE-209 is evaluated and proposed as internal surrogate standard for the determination of BDE-209 in mass spectrometric detection in electron capture negative ionization (ECNI) mode.

  • 46. Blomqvist, Per
    et al.
    McNamee, Margaret Simonson
    Stec, Anna A.
    Gylestam, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Detailed study of distribution patterns of polycyclic aromatic hydrocarbons and isocyanates under different fire conditions2014In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 38, no 1, p. 125-144Article in journal (Refereed)
    Abstract [en]

    This study has examined the distribution patterns between gas phase and particle phase of some chemical compounds produced in fires. It has also addressed the question of the distribution of individual particle-associated species between the different size-ranges of particles. The chemical compounds studied and discussed in this paper are polycyclic aromatic hydrocarbons (PAHs), and isocyanates. The steady-state tube furnace, ISO/TS 19700, was chosen as the physical fire model in order to study the production of particles from different types of fire exposure, that is, oxidative pyrolysis, well-ventilated flaming fires and under-ventilated flaming post-flashover fires. Two materials were chosen for investigation, a polyvinyl chloride (PVC) carpet and a wood board. The particle production from the two materials investigated varied concerning both the amounts produced and the particle size distributions. The analysis of PAHs showed that volatile PAHs were generally dominant. However, when the toxicity of the individual species was taken into account, the relative importance between volatile and particle-associated PAHs shifted the dominance to particle-bound PAH for both materials. The substantial degradation in the tests of the low polyurethane content of the PVC carpet, and the (4,4-methylenediphenyl diisocyanate)-based binder in the wood board resulted in no or very small amount of quantifiable diisocyanates.

  • 47. Blomqvist, Per
    et al.
    Simonson McNamee, Margaret
    Stec, Anna A.
    Gylestam, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Characterisation of fire generated particles: BRANDFORSK project 700-061, FireTechnology, SP Report 2010:012010Report (Other academic)
    Abstract [en]

    Characterisation of fire generated particles

    The present project has examined the question of distribution patterns of important chemical compounds between gas phase and particle phase. It has also, in some cases, addressed the question of the distribution of individual particle-associated species between the different size-ranges of particles produced in a fire. The chemical compounds studied were hydrogen chloride (HCl), polycyclic aromatic hydrocarbons (PAHs), and isocyanates.

    The steady-state tube furnace, ISO/TS 19700, was chosen as the physical fire model in order to study the production of particles from different types of fire exposure. Three different fire types were investigated: oxidative pyrolysis, well-ventilated flaming fires and vitiated post flashover. Two materials were chosen for investigation, PVC-carpet and wood board, based on their prevalence fire exposure scenarios and their chemical composition. The particle production from the two materials investigated varied both concerning the amounts produced and the particle size distributions. The production of particles on a mass basis was generally significantly lower from the wood board compared with the PVC-carpet. The tests with the PVC-carpet showed that relatively large particles are produced from all combustion conditions examined. The tests made with the wood board show preferably predisposition towards the production of small-sized particles during flaming combustion.

    The analysis of PAHs in the tests with the PVC-carpet showed that volatile PAHs were dominate during all types of combustion. However, when the toxicity of the individual species was taken into account, the relative importance between volatile and particle associated PAHs changed. From the tests with the wood board material (OSB) it was noted that the highest yields of total PAHs were found from under ventilated conditions, and the volatile part of the total PAH dominated for this material as well. The yields found from the well-ventilated tests were very low. Toxicity weighted data showed that the particle associated part dominated the toxicity both for under ventilated and well-ventilated conditions.

    A study made of the presence of chlorine on particles showed that it is clear that the major part of the HCl produced during combustion of the PVC-carpet is present in the gas phase. Chlorine was found associated with particulates but these results were, however, inconclusive due to the difficulty in determining the source of the chlorine found in the soot fractions studied.

    The low polyurethane (PUR) content and the substantial degradation of the PUR in the tests resulted in no or very small amounts of quantifiable isocyanate dimers (i.e. high molecular species). Monoisocyanates such as ICA and MIC dominated in the emitted degradation products. These kinds of monoisocyanates are volatile compounds and almost exclusively present in the gas phase.

     

  • 48. Bogdal, Christian
    et al.
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Diefenbacher, Pascal S.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Berger, Urs
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Fast Quantification of Chlorinated Paraffins in Environmental Samples by Direct Injection High-Resolution Mass Spectrometry with Pattern Deconvolution2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 5, p. 2852-2860Article in journal (Refereed)
    Abstract [en]

    Chlorinated paraffins (CPs) are high production volume chemicals, but data about their environmental fate are scarce. CP mixtures composed of thousands of isomers represent a major challenge for quantification at low levels in environmental samples. Here, we present a novel analytical method for analysis of short-chain, medium-chain, and long-chain CPs in a single injection, that also yields information about congener group pattern. Our detection method is based on direct injection into an atmospheric pressure chemical ionization source operated in negative ion mode under chlorine-enhanced conditions, followed by quadrupole time-of-flight high-resolution mass spectrometry (APCI-qTOF-HRMS) operated in full-scan mode. A mathematical algorithm is applied to deconvolute the CP patterns in the analyzed samples into a linear combination of patterns of technical CP mixtures and to quantify CPs using technical mixtures as external calibration standards. For CP mixtures with known composition, the new method provided concentrations that were within a factor of 1.2 of the target value. Accuracies for CPs spiked to sediment and fish extracts were between 91% and 123%. Concentrations determined in unspiked field samples were within a factor of 5 for short-chain CPs and a factor of 16 for medium-chain CPs of results obtained with an independent method based on gas chromatography/electron capture negative ionization high-resolution mass spectrometry (GC/ECNI-HRMS). The presented APCI-qTOF-HRMS pattern deconvolution method is an interesting alternative for CP analysis in environmental samples. It is particularly sensitive for medium- and long-chain CPs and has the advantage of being extremely fast (instrumental analysis time, less than 1 min).

  • 49. Boman, Christoffer
    et al.
    Pettersson, Esbjorn
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bostrom, Dan
    Nordin, Anders
    Stove Performance and Emission Characteristics in Residential Wood Log and Pellet Combustion, Part 1: Pellet Stoves2011In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, p. 307-314Article in journal (Refereed)
    Abstract [en]

    Stove performance, characteristics, and quantities of gaseous and particulate emissions were determined for two different pellet stoves, varying fuel load, pellet diameter, and chimney draft. This approach aimed at covering variations in emissions from stoves in use today. The extensive measurement campaign included CO, NO(x), organic gaseous carbon, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), total particulate matter (PM(tot)) as well as particle mass and number concentrations, size distributions, and inorganic composition. At high load, most emissions were similar. For stove B, operating at high residual oxygen and solely with primary air, the emissions of PM,, and particle numbers were higher while the particles were smaller. Lowering the fuel load, the emissions of CO and hydrocarbons increased dramatically for stove A, which operated continuously also at lower fuel loads. On the other hand for stove B, which had intermittent operation at lower fuel loads, the emissions of hydrocarbons increased only slightly lowering the fuel load, while CO emissions increased sharply, due to high emissions at the end of the combustion cycle. Beside methane, dominating VOCs were ethene, acetylene, and benzene and the emissions of VOC varied in the range 1.1-42 mg/MJ(fuel). PAH emissions (2-340 mu g/MJ(fuel)) were generally dominated by phenanthrene, fluoranthene and pyrene. The PM(tot) values (15-45 mg/MJ(fuel)) were in all cases dominated by fine particles with mass median diameters in the range 100-200 nm, peak mobility diameters of 50-85 nm, and number concentrations in the range 4 x 10(13) to 3 x 10(14) particles/MJ(fuel). During high load conditions, the particulate matter was totally dominated by inorganic particles at 15-25 mg/MJ(fuel) consisting of potassium, sodium, sulfur, and chlorine, in the form of K(2)SO(4), K(3)Na(SO(4))(2), and KCl. The study shows that differences in operation and modulation principles for the tested pellet stoves, relevant for appliances in use today, will affect the performance and emissions significantly, although with lower scattering in the present study compared to compiled literature data.

  • 50.
    Carlsson, Henrik
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholms Universitet, MMK.
    Development of an adductomic approach to identify electrophiles in vivo through their hemoglobin adducts2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Humans are exposed to electrophilically reactive compounds, both formed endogenously and from exogenous exposure. Such compounds could react and form stable reaction products, adducts, at nucleophilic sites in proteins and DNA. The formation of adducts constitutes a risk for effects, such as cancer and contact allergy, and plays a role in ageing processes. Adducts to proteins offer a possibility to measure electrophilic compounds in vivo.

    Adductomic approaches aim to study the totality of adducts, to specific biomolecules, by mass spectrometric screening. This thesis describes the development and application of an adductomic approach for the screening of unknown adducts to N-terminal valine (Val) in hemoglobin (Hb) by liquid chromatography tandem mass spectrometry (LC/MS/MS).

    The adductomic approach is based on the FIRE procedure, a modified Edman procedure for the analysis of adducts to N-terminal Val in Hb by LC/MS/MS. The adduct screening was performed by stepwise scanning of precursor ions in small mass increments and monitoring four fragments common for derivatives of detached Val adducts, in the multiple reaction monitoring mode. Samples from 12 smokers/nonsmokers were screened with the adductomic approach, and seven previously identified adducts and 19 unknown adducts were detected. A semiquantitative approach was applied for approximate quantification of adduct levels.

    A strategy for identifying unknown Hb adducts using adductome LC/MS/MS data was formulated and applied for the identification of unknown adducts. Identifications were based on the observed m/z of precursor ions and retention times combined with databases and Log P calculations. Hypothesized adducts were generated in vitro for comparison and matching with the corresponding unknown adducts. Five identified adducts correspond to the precursor electrophiles ethyl vinyl ketone (EVK), glyoxal, methylglyoxal, acrylic acid, and 1-octen-3-one. These adducts, except the adducts corresponding to glyoxal and methylglyoxal, have not been observed as protein adducts before.  Probable exposure sources to these electrophiles are diet and/or endogenous formation. The observation of these adducts motivate further studies to evaluate possible contributions to health risks, as well as their potential as biomarkers of exposure.

    The adduct from EVK was quantitatively assessed through different experiments to estimate the daily internal dose (area under the concentration-time-curve, AUC). EVK is about 2 × 103 more reactive than the reference compound acrylamide. The EVK adduct was shown to be unstable, with a relatively short half-life. The daily AUC in humans of EVK was estimated to be about 20 times lower than the corresponding AUC of acrylamide from intake via food.

    To confirm the observation of the detected unknown adducts and obtain a statistical foundation, analysis of unknown adducts were performed in large sets of blood samples (n = 50–120) from human cohorts. The majority of the previously detected unknown adducts were found in all analyzed samples, and the levels of many adducts showed large variations between individuals. The cause and significance of these observed variations are not yet clarified, but are of importance for the directions of future studies.

    In conclusion, a new approach for identification of unknown human exposure to electrophiles was developed and successfully applied. 

123456 1 - 50 of 279
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf