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  • 101.
    Forshed, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Idborg, Helena
    Jacobsson, Sven P.
    Evaluation of different techniques for fusion of LC/MS and 1HNMR data2007In: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 85, no 1, p. 102-109Article in journal (Refereed)
    Abstract [en]

    In the analyses of highly complex samples (for example, metabolic fingerprinting), the data might not suffice for classification when using only a single analytical technique. Hence, the use of two complementary techniques, e.g., LUMS and H-1-NMR, might be advantageous. Another possible advantage from using two different techniques is the ability to verify the results (for instance, by verifying a time trend of a metabolic pattern). In this work, both LC/MS and H-1-NMR data from analysis of rat urine have been used to obtain metabolic fingerprints. A comparison of three different methods for data fusion of the two data sets was performed and the possibilities and difficulties associated with data fusion were discussed. When comparing concatenated data, full hierarchical modeling, and batch modeling, the first two approaches were found to be the most successful. Different types of block scaling and variable scaling were evaluated and the optimal scaling for each case was found by cross validation. Validations of the final models were performed by means of an external test set.(2)

  • 102.
    Forshed, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Schuppe-Koistinen, Ina
    Jacobsson, Sven P.
    Peak alignment of NMR signals by means of a genetic algorithm2003In: Analytica Chimica Acta, ISSN 0003-2670, Vol. 487, no 2, p. 189-199Article in journal (Refereed)
  • 103.
    Forshed, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Stolt, Ragnar
    Idborg, Helena
    Jacobsson, Sven P.
    Enhanced multivariate analysis by correlation scaling and fusion of LC/MS and 1H-NMR data2007In: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 85, no 2, p. 179-185Article in journal (Refereed)
    Abstract [en]

    A method to enhance the multivariate data interpretation of, for instance, metabolic profiles is presented. This was done by correlation scaling of 1H NMR data by the time pattern of drug metabolite peaks identified by LC/MS, followed by parallel factor analysis (PARAFAC). The variables responsible for the discrimination between the dosed and control rats in this model were then eliminated in both data sets. Next, an additional PARAFAC analysis was performed with both LC/MS and 1H NMR data, fused by outer product analysis (OPA), to obtain sufficient class separation. The loadings from this second PARAFAC analysis showed new peaks discriminating between the classes. The time trajectories of these peaks did not agree with the drug metabolites and were detected as possible candidates for markers. These data analyses were also compared with the PARAFAC analysis of raw data, which showed very much the same loading peaks as for the correlation-scaled data, although the intensities differed. Elimination of the variables correlated with the drug metabolites was therefore necessary to be able to select the peaks which were not drug metabolites and which discriminated between the classes.1

  • 104.
    Forshed, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Åberg, K. Magnus
    Karlberg, Bo
    Lindberg, Johan
    Jacobsson, Sven P.
    A comparison of methods for alignment of NMR peaks in the context of cluster analysis2005In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, Vol. 38, no 5, p. 824-832Article in journal (Refereed)
  • 105. Frick-Engfeldt, M
    et al.
    Zimerson, E
    Karlsson, D
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, G
    Isaksson, M
    Bruze, M
    Is it possible to improve the patch-test diagnostics for isocyanates? A stability study of petrolatum preparations of diphenylmethane-4,4-diisocyanate and polymeric diphenylmethane diisocyanate2007In: Contact Dermatitis, Vol. 56, p. 27–34-Article in journal (Refereed)
  • 106. Gad, Helge
    et al.
    Svensson, Linda M.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Saleh, Aljona
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Berntsson, Ronnie P.-A.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Gustafsson, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Johansson, Fredrik
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Djureinovic, Tatjana
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Häggblad, Maria
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Martens, Ulf
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Lundgren, Bo
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Granelli, Ingrid
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Stenmark, Pål
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Helleday, Thomas
    MTH1 inhibition eradicates cancer by preventing sanitation of the dNTP pool2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 508, no 7495, p. 215-221Article in journal (Refereed)
    Abstract [en]

    Cancers have dysfunctional redox regulation resulting in reactive oxygen species production, damaging both DNA and free dNTPs. The MTH1 protein sanitizes oxidized dNTP pools to prevent incorporation of damaged bases during DNA replication. Although MTH1 is non-essential in normal cells, we show that cancer cells require MTH1 activity to avoid incorporation of oxidized dNTPs, resulting in DNA damage and cell death. We validate MTH1 as an anticancer target in vivo and describe small molecules TH287 and TH588 as first-in-class nudix hydrolase family inhibitors that potently and selectively engage and inhibit the MTH1 protein in cells. Protein co-crystal structures demonstrate that the inhibitors bind in the active site of MTH1. The inhibitors cause incorporation of oxidized dNTPs in cancer cells, leading to DNA damage, cytotoxicity and therapeutic responses in patient-derived mouse xenografts. This study exemplifies the non-oncogene addiction concept for anticancer treatment and validates MTH1 as being cancer phenotypic lethal.

  • 107.
    Gao, Qiuju
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Monosaccharide compositional analysis of marine polysaccharides by hydrophilic interaction liquid chromatography-tandem mass spectrometry2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 7, p. 2517-2529Article in journal (Refereed)
    Abstract [en]

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

  • 108. Grey, Carl
    et al.
    Edebrink, Per
    Krook, Maria
    Jacobsson, Sven P.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Development of a high performance anion exchange chromatography analysis for mapping of oligosaccharides2009In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 877, no 20-21, p. 1827-1832Article in journal (Refereed)
    Abstract [en]

    In the present study a HPAEC-PAD method is described that was developed for monitoring the consistency of N-glycosylation during the production and purification of recombinant proteins and monoclonal antibodies. The method successfully separated 18 neutral and sialylated oligosaccharides. Results obtained were compared with MALDI-TOF MS and it was shown that both methods gave similar results. in addition, a method validation was performed showing that the HPAEC-PAD analysis was well suited for the mapping and characterization of oligosaccharides. The method was found to be robust and additionally the precision was significantly better compared to the MALDI-TOF MS method. 

  • 109. Gustafsson, P
    et al.
    Östman, C
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sällsten, G
    Indoor levels of polycyclic aromatic hydrocarbons in homes with or without wood burning for heating2008In: Environmental Science & Technology, Vol. 42, p. 5074-5080Article in journal (Refereed)
  • 110.
    Gustavsson, Marcus
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Meiby, Elinor
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Gylestam, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dahlin, Jakob
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Spanne, Mårten
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dalene, Marianne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Tveterås, Björn Oscar
    Pedersen, Age Engen
    Adsorption Efficiency of Respirator Filter Cartridges for Isocyanates2010In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 54, no 4, p. 377-390Article in journal (Refereed)
    Abstract [en]

    In some industries, the temperature and the humidity will vary greatly between different work places, such as outdoor work in arctic or tropical climates. There is therefore a need to test respirator filters at conditions that simulate conditions that are relevant for the industries that they are used in. Filter cartridges were exposed to controlled atmospheres of varying isocyanate concentration, air humidity, and temperature in an exposure chamber. For isocyanic acid (ICA) and methyl isocyanate (MIC), the exposure concentrations were between 100 and 200 p.p.b., monitored using a proton transfer reaction mass spectrometer. ICA and MIC were generated by continuous thermal degradation of urea and dimethylurea. The breakthrough was studied by collecting air samples at the outlet of the filter cartridges using impinger flasks or dry samplers with di-n-butylamine as derivatization reagent for isocyanates followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. For hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), the exposure concentrations were between 4 and 20 p.p.b. and were generated by wet membrane permeation. To reveal the profile of adsorption in different layers of the respirator filters, representative samples from each of the layers were hydrolyzed. The hydrolysis products hexamethylene diamine and isophorone diamine were determined after derivatization with pentafluoropropionic anhydride (PFPA) followed by LC-MS/MS analysis. The two filter types studied efficiently absorbed both ICA and MIC. There was no trend of impaired performance throughout 48-h exposure tests. Even when the filters were exposed to high concentrations (similar to 200 p.p.b.) of ICA and MIC for 96 h, the isocyanates were efficiently absorbed with only a limited breakthrough. The majority of the HDI and IPDI (> 90%) were absorbed in the top layers of the absorbant, but HDI and IPDI penetrated farther down into the respirator filters during 120 h of exposure as compared to 16 h exposure.

  • 111.
    Gylestam, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Isocyanates - methodology for gas and particle generation, sampling and detection2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Isocyanates are mainly used in the industry for the production of polyurethane (PUR) plastics. Workers are at risk of being exposed during the manufacturing of PUR. During thermal degradation of PUR, isocyanates are released and workers involved in hot work such as fire-fighting, welding etc. may also be exposed.

    Isocyanates are known to cause allergic diseases and are the most common cause of occupational asthma. Some of the isocyanates used are suspected human carcinogens. Exposure among workers occurs frequently.

    Isocyanates are reactive unstable compounds that need to be converted to stabile derivatives immediately during sampling to avoid underestimation of the exposure. Di-n-ButylAmine (DBA) was used as derivatising reagent to form stable urea derivatives. The DBA derivatives were analysed using LC-MS/MS.

    In this thesis a novel technology for the direct monitoring of isocyanates using a Proton Transfer Reaction Mass Spectrometry (PTR-MS) is presented. Advancement of technology for the generation of isocyanates in an environmental chamber, dry sampling, particle-size fractionated sampling and the testing of respirator filter cartridges are described.

    The dry sampler was demonstrated to be robust and enabled sampling up to 32 h. Precise sampling without the need of field extraction was made possible.

    The particle-size fractionated sampling efficiently separated gas-phase and respirable particle-borne isocyanates (< 4µm in diameter).

    Two personal protective respirator filter cartridges were studied. No trend of impaired performance for mono-isocyanates throughout 48-h exposure tests was found.

    The distribution patterns, in a steady-state tube-furnace oven, between gas phase and different particle-phase fractions of isocyanates produced in fires were investigated. The substantial degradation of a PVC-carpet containing PUR and a wood board with a MDI based binder resulted mainly in the formation of high levels of monoisocyanates.

  • 112.
    Gylestam, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Gustavsson, Marcus
    Karlsson, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. Institutet för Kemisk Analys Norden AB, Sweden.
    Dalene, Marianne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. Institutet för Kemisk Analys Norden AB, Sweden.
    Skarping, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sampling of Respirable Isocyanate Particles2014In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 58, no 3, p. 340-354Article in journal (Refereed)
    Abstract [en]

    An advanced design of a denuder impactor (DI) sampler has been developed for characterization of possible airborne isocyanate exposure in different particle size fractions. The sampler is equipped with 12 different parallel denuder tubes, 4 impaction stages with the cut-off values (d50) of: 9.5, 4, 2.5 and 1 µm, and an end filter that collects particles < 1 µm. All collecting parts were impregnated with di-n-butylamine DBA as the reagent in a mixture with acetic acid. The performance of the DI sampler was studied on a standard atmosphere containing gas and particulate isocyanates. The isocyanate atmosphere was generated by liquid permeation of 2,4-, 2,6-Toluene Diisocyanate (TDI), 1,6-Hexamethylene Diisocyanate (HDI) and Isophorone Diisocyanate (IPDI). 4,4’-Methylene Diphenyl Diisocyanate (MDI) particles were generated by heating of technical MDI and condensing the mixture of gas and particle-borne MDI in an atmosphere containing mixed salt particles. The study was performed in a 0.85 m3 environmental chamber with stainless steel walls. With the advancement of the DI sampler it is now possible to collect isocyanate particle samples for up to 320min. The performance of the DI sampler is essentially unaffected by the humidity. The DI sampler and the ASSET™ EZ4-NCO sampler (Sigma-Aldrich/Supelco, Bellefonte, PA, USA) gave similar results. Sample losses within the DI sampler are low. In the environmental chamber it was observed that the particle distribution may be affected by the humidity and ageing. A scanning mobility particle sizer (SMPS) was used to separate a flow of selected fractions containing MDI particles from mixed MDI and salt particles. The particle-size distribution had a maximum at about 300nm, but later in the environmental chamber 1 µm dominated. The distribution was very different as compared to with only NaCl or MDI present. The biological relevance for studying isocyanate nano particles is significant as these have the possibility to reach the lower airways where allergic reactions may occur. SMPS and isocyanate air sampling can be used for the investigation of isocyanate nano particles.

  • 113.
    Gylestam, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dalene, Marianne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of Gas Phase Isocyanates Using Proton Transfer Reaction Mass Spectrometry2011In: Analytical Chemistry Letters, ISSN 2229-7928, Vol. 1, no 4, p. 261-271Article in journal (Refereed)
    Abstract [en]

    We report the development of proton transfer reaction-mass spectrometry (PTR-MS) methodology for on-line monitoring, using a direct reading instrument, of several typical gas phase isocyanates, including isocyanic acid (ICA), ethyl isocyanate (EIC), phenyl isocyanate (PhI), hexamethylene diisocyanate (HDI) and toluene diisocyanate (TDI). In the study, ICA and MIC were generated by thermal degradation of urea and 1,3-dimethylurea, respectively, while the other isocyanates were generated by liquid and gas permeation techniques. Comparative, reference measurements were made by sampling isocyanate atmosphere using impinger flasks containing the reagent di-n-butyl amine (DBA) then determining the resulting DBA derivatives by liquid chromatography (LC)-MS/MS. Reproducible measurements were obtained, with a <10 % drift in PTR-MS responses during a 12 month period. Further, there were linear correlations (R2>0.99) between the data acquired by the PTR-MS technique and air sampling followed by LC-MS/MS for all tested isocyanates in the concentration range 2-100 ppb, with a PTR-MS detection limits in the low ppb range. For all isocyanates except EIC, BIC, HDI and IPDI, the protonated molecular ions were the most abundant ions in the PTR mass spectra. Overall, the results show that the developed method enables sensitive, time-resolved measurements of airborne isocyanates to be acquired over several weeks.

  • 114.
    Gylestam, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Riddar, Jakob B.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dahlin, Jakob
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dalene, Marianne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dry Sampling of Gas-Phase Isocyanates and Isocyanate Aerosols from Thermal Degradation of Polyurethane2014In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 58, no 1, p. 28-49Article in journal (Refereed)
    Abstract [en]

    The performance of a dry sampler, with an impregnated denuder in series with a glass fibre filter, using di-n-butylamine (DBA) for airborne isocyanates (200ml min−1) is investigated and compared with an impinger flask with a glass fibre filter in series (1 l min−1). An exposure chamber containing 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and 2,4- and 2,6-toluene diisocyanate (TDI) in the concentration range of 5–205 μg m−3 [0.7–33 p.p.b.; relative humidity (RH) 50%], generated by gas- and liquid-phase permeation, was used for the investigation. The precision for the dry sampling for five series with eight samplers were in the range of 2.0–6.1% with an average of 3.8%. During 120-min sampling (n = 4), no breakthrough was observed when analysing samplers in series. Sixty-four exposed samplers were analysed after storage for 0, 7, 14, and 21 days. No breakdown of isocyanate derivatives was observed. Twenty-eight samplers in groups of eight were collecting isocyanates during 0.5–32h. Virtually linear relationships were obtained with regard to sampling time and collected isocyanates with correlation coefficients in the range of 0.998–0.999 with the intercept close to the origin. Pre- or post-exposure to ambient air did not affect the result. Dry sampling (n = 48) with impinger-filter sampling (n = 48) of thermal decomposition product of polyurethane polymers, at RH 20, 40, 60, and 90%, was compared for 11 isocyanate compounds. The ratio between the different isocyanates collected with dry samplers and impinger-filter samplers was in the range of 0.80–1.14 for RH = 20%, 0.8–1.25 for RH = 40%, 0.76–1.4 for RH = 60%, and 0.72–3.7 for RH = 90%. Taking into account experimental errors, it seems clear that isocyanic acid DBA derivatives are found at higher levels in the dry samples compared with impinger-filter samplers at elevated humidity. The dry sampling using DBA as the reagent enables easy and robust sampling without the need of field extraction.

  • 115.
    Hansson, Helena
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A Novel Miniaturised Dynamic Hollow-Fibre Liquid-Phase Micro-Extraction Method for Xenobiotics in Human Plasma Samples2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bioanalytical chemistry is a challenging field, often involving complex samples, such as blood, plasma, serum or urine. In many applications, sample cleanup is the most demanding and time-consuming step.

    In the work underlying this thesis a novel dynamic miniature extractor, known as a hollow-fibre liquid-phase microextractor (HF-LPME), was designed, evaluated and studied closely when used to clean plasma samples. Aqueous-organic-aqueous liquid extraction, in which the organic liquid is immobilised in a porous polypropylene membrane, was the principle upon which the extractor was based, and this is discussed in all the papers associated with this thesis. This type of extraction is known as supported-liquid membrane extraction (SLM). The aim of this work was the development of a dynamic system for SLM. It was essential that the system could handle small sample volumes and had the potential for hyphenations and on-line connections to, for instance, LC/electrospray-MS. The design of a miniaturised HF-LPME device is presented in Paper I. The extraction method was developed for some weakly acidic pesticides and these were also used for evaluation. In the work described in Paper II, the method was optimised on the basis of an experimental design using spiked human plasma samples. Paper III presents a detailed study of the mass-transfer over the liquid membrane. The diffusion through the membrane pores was illustrated by a computer-simulation. Not surprisingly, the more lipophilic, the greater the retention of the compounds, as a result of dispersive forces. The main focus of the work described in Paper IV was to make the HF/LPME system more versatile and user-friendly; therefore, the extractor was automated by hyphenation to a SIA system.

  • 116.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Study of mass transfer in a dynamic hollow-fibreliquid phase microextraction system2010In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 33, no 1, p. 112-119Article in journal (Refereed)
    Abstract [en]

    The extraction characteristics of a dynamic hollow-fibre liquid phase microextractionsystem were investigated by studying the mass transfer and diffusion rates of dinitrophenolsfrom plasma samples over the liquid membrane (dihexylether). The measureddiffusion coefficients were compared with theoretical values calculated from Stokesdiameters. The diffusion mechanism was simulated by computer and the most polarcompounds, 2,4-dinitrophenol and 4,6-o-dinitrocresol, had associated diffusion coefficientsthat were close to the calculated theoretical values. 2-sec-Butyl-4,6 dinitrophenoland 2-tert-butyl-4,6-dinitrophenol, the compounds with the highest log P values, wereretained by the polypropylene membrane, which reduced the experimentally observeddiffusion rates to about half of the theoretical values. The retention was most likely due todispersive forces interacting with the pore inner walls. Extraction was linearly correlatedwith time for all compounds and the repeatability was high (RSDs 7–11%), even for theshortest extraction times. Method LOD as the amount injected ranged between 0.3 and3.1 ng for an extraction cycle of 213 s.

  • 117.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic hollow-fibre liquid phase microextraction for human plasma samples automated by sequential injection analysisManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents an easily handled, hollow-fibre liquid phase microextraction (HF-LPME) sample clean-up method, automated by the use of a programmable sequential injection analysis (SIA) system. Use of a SIA system significantly reduces the need for manual sample handling. This new type of clean-up system was assessed and compared with manual HF-LPME for the extraction of acidic compounds (dinitrophenols) from human plasma, in terms of human intervention requirements, efficiency, repeatability and carry-over. Its application to a SIA system for basic compounds (b-blockers) is also presented. The sample aliquots collected off-line from the SIA system were subsequently subjected to separation with LC and the various analytes were detected with ESI-MS.

    Extraction efficiency values between 28 and 56% (RSD 5-10%, n = 7) were achieved for the dinitrophenol compounds after an extraction cycle of 58 min including a 30 min washing step. According to the MS analysis the SIA/HF-LPME method yielded clean chromatograms with no detectable interfering peaks. Ion suppression in positive ESI-MS was between 4 and 21% when tested on extracts with b-blockers.

  • 118.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Lagerstroem, Malene
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic hollow-fibre liquid phase microextraction of dinitrophenols from human plasma: Optimization of an extraction flow system using experimental design methodology2009In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 79, no 3, p. 633-638Article in journal (Refereed)
    Abstract [en]

    The utility of a dynamic hollow-fibre liquid phase microextraction method (optimized using a four-variable experimental design and response surface modelling) for extracting dinitrophenolic compounds from human plasma samples was evaluated. The investigated variables were donor phase salt concentration (10–400 mM), donor phase pH (2–6), acceptor phase pH (7–12), and donor/acceptor phase flow rates (30/7.5 to 70/17.5 μL min−1). Four dinitrophenol pesticides were used as model substances at concentrations of 0.1 μg mL−1 in spiked human plasma samples. Extraction efficiencies ranging from 42 to 77% with RSDs below 9 were achieved with the optimized method. The flow rate and acceptor pH were shown to strongly affect the extraction efficiency for all compounds, while the donor phase pH and salt concentration had minor effects. With a well-defined acceptor phase pH and flow rate the system exhibited high robustness. The limits of quantification for the investigated compounds, using the presented extraction method followed by liquid chromatography/electrospray ionization mass spectrometry in selected ion monitoring mode, ranged from 0.05 to 0.1 μg mL−1 plasma.

  • 119.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Assessment of a dynamic hollow-fibre liquid phase microextraction system forhuman blood plasma samples2009In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 77, no 4, p. 1309-1314Article in journal (Refereed)
    Abstract [en]

    A dynamic liquid phase microextraction (LPME) system, based on hollow-fibre supported liquid membrane(SLM) extraction, was developed for extracting ionisable xenobiotics from human plasma, andits performance was evaluated (in terms of extraction efficiency, reproducibility, durability and carryover)using nitrophenolic compounds as model analytes at concentrations of 0.1–0.5gmL−1 in aqueousstandards. The efficiency and repeatability were tested also on spiked human plasma. The system isnon-expensive, convenient, requires minimal manual handling and enables samples with volumes assmall as 0.2mL to be extracted. For plasma samples extraction efficiencies of between 30 and 58% wereachieved within 20 min, including washing steps. The limit of detection (LOD) values were in the range0.02–0.03gmL−1. The developed system can provide enrichment factors up to eight, based on theinjection-to-acceptor volume ratio (in this case 0.2–0.025 mL). The same hollow-fibre membrane wasused up to 8 days with no loss of efficiency. Carry-over was lower than detection limit.

  • 120. Harrad, Stuart
    et al.
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Abdallah, Mohamed Abou-Elwafa
    Bergh, Caroline
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Björklund, Justina A.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Covaci, Adrian
    Darnerud, Per Ola
    de Boer, Jacob
    Diamond, Miriam
    Huber, Sandra
    Leonards, Pim
    Mandalakis, Manolis
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Haug, Line Smastuen
    Thomsen, Cathrine
    Webster, Thomas F.
    Indoor Contamination with Hexabromocyclododecanes, Polybrominated Diphenyl Ethers, and Perfluoroalkyl Compounds: An Important Exposure Pathway for People?2010In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 44, no 9, p. 3221-3231Article, review/survey (Refereed)
    Abstract [en]

    This review underlines the importance of indoor contamination as a pathway of human exposure to hexabromocyclododecanes (HBCDs), polybrominated diphenyl ethers (PBDEs), and perfluoroalkyl compounds (PFCs). There is ample evidence of substantial contamination of indoor dust with these chemicals and that their concentrations in indoor air exceed substantially those outdoors. Studies examining the relationship between body burden and exposure via indoor dust are inconsistent while some indicate a link between body burdens and PBDE and HBCD exposure via dust ingestion, others find no correlation. Likewise, while concentrations in indoor dust and human tissues are both highly skewed, this does not necessarily imply causality. Evidence suggests exposure via dust ingestion is higher for toddlers than adults. Research priorities include identifying means of reducing indoor concentrations and indoor monitoring methods that provide the most ""biologically-relevant"" measures of exposure as well as monitoring a wider range of microenvironment categories. Other gaps include studies to improve understanding of the following: emission rates and mechanisms via which these contaminants migrate from products into indoor air and dust; relationships between indoor exposures and human body burdens; relevant physicochemical properties; the gastrointestinal uptake by humans of these chemicals from indoor dust; and human dust ingestion rates.

  • 121.
    Hessle, Viktoria
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Björk, Petra
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Sokolowski, Marcus
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Gonzalez de Valdivia, Ernesto
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Silverstein, Rebecca
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Artemenko, Konstantin
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Tyagi, Anu
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Maddalo, Gianluca
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Helbig, Roger
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Zubarev, Roman A
    Visa, Neus
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    The exosome Associates Cotranscriptionally with the Nascent Pre-mRNP through Interactions with Heterogeneous Nuclear Ribonucleoproteins2009In: Molecular Biology of the Cell, ISSN 1059-1524, E-ISSN 1939-4586, Vol. 20, no 15, p. 3459-3470Article in journal (Refereed)
    Abstract [en]

    Eukaryotic cells have evolved quality control mechanisms to degrade aberrant mRNA molecules and prevent the synthesis of defective proteins that could be deleterious for the cell. The exosome, a protein complex with ribonuclease activity, is a key player in quality control. An early quality checkpoint takes place cotranscriptionally but little is known about the molecular mechanisms by which the exosome is recruited to the transcribed genes. Here we study the core exosome subunit Rrp4 in two insect model systems, Chironomus and Drosophila. We show that a significant fraction of Rrp4 is associated with the nascent pre-mRNPs and that a specific mRNA-binding protein, Hrp59/hnRNP M, interacts in vivo with multiple exosome subunits. Depletion of Hrp59 by RNA interference reduces the levels of Rrp4 at transcription sites, which suggests that Hrp59 is needed for the exosome to stably interact with nascent pre-mRNPs. Our results lead to a revised mechanistic model for cotranscriptional quality control in which the exosome is constantly recruited to newly synthesized RNAs through direct interactions with specific hnRNP proteins.

  • 122.
    Hofer, Sabine
    et al.
    Department of Biology, University of Marburg, D-35032 Marburg, Germany.
    Dircksen, Heinrich
    Stockholm University, Faculty of Science, Department of Zoology, Functional Morphology.
    Tollbäck, Petter
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Homberg, Uwe
    Department of Biology, University of Marburg, D-35032 Marburg, Germany.
    Novel insect orcokinins: characterization and neuronal distribution in the brains of selected dicondylian insects.2005In: Journal of Comparative Neurology, ISSN 0021-9967, E-ISSN 1096-9861, Vol. 490, no 1, p. 57-71Article in journal (Refereed)
    Abstract [en]

    Orcokinins are a family of myotropic neuropeptides identified in various decapod crustaceans and recently in a cockroach. Their presence in the crustacean nervous system and hemolymph suggests that they act as hormones and as locally acting neuromodulators. To provide further evidence for the existence of orcokinins in insects, we identified a novel orcokinin-related peptide in the locust Schistocerca gregaria and used an antiserum against Asn13-orcokinin for immunostaining in the brains of selected dicondylian insects, including a silverfish, three polyneopteran species (a cockroach and two locusts), and three endopterygote species (a moth, a bee, and a fly). As analyzed by MALDI-TOF spectrometry and nanoelectrospray Q-TOF, the locust orcokinin is a novel tetradecapeptide with striking sequence similarity to crustacean orcokinins. Orcokinin immunostaining was widespread and occurred in similar patterns in the brain of the silverfish and the polyneopteran species. Prominent immunostaining was detected in the optic lobe, especially in the medulla and in the accessory medulla, in local interneurons of the antennal lobe, and in extrinsic and intrinsic mushroom-body neurons. All parts of the central complex and many other areas of the brains were densely stained. In the silverfish, the cockroach, and the locusts, processes in the corpora cardiaca showed orcokinin immunoreactivity, suggesting that orcokinins also serve a hormonal role. In contrast to the case in polyneopteran species, immunostaining was completely lacking in the brains of the honeybee, fruitfly, and sphinx moth. This indicates that orcokinins either are modified considerably or may be completely absent in the brains of endopterygote insects.

  • 123. Holmgren, Erik
    et al.
    Ek, Stefan
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Extraction of explosives from soil followed by gas chromatography-mass spectrometry analysis with negative chemical ionization2012In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1222, p. 109-115Article in journal (Refereed)
    Abstract [en]

    A new, simple and accurate method for extraction of explosives from soil was developed and validated. The method includes one hour gentle extraction of compounds from soil in acetonitrile:dichloromethane 50:50 at 30 degrees C. Further analysis was made with GC-MS using cool on-column injection and negative chemical ionization. The method increased the recovery of the more volatile products, generated higher accuracy and was extensively time-saving compared to the conventional EPA (US Environmental Protection Agency) 8330 method. Applications are demonstrated on commercial reference materials.

  • 124. Horvai, G.
    et al.
    Worsfold, P.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, J. E. T.
    Analytical chemistry and bioanalytical chemistry - A yet unshaped social relationship2011In: TrAC. Trends in analytical chemistry, ISSN 0165-9936, E-ISSN 1879-3142, Vol. 30, no 3, p. 422-424Article in journal (Refereed)
  • 125. Horvai, George
    et al.
    Worsfold, Paul
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, Jens E. T.
    European analytical column no. 392011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 400, no 6, p. 1539-1541Article in journal (Refereed)
  • 126. Horvai, George
    et al.
    Worsfold, Paul
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, Jens E. T.
    European Analytical Column No. 39 Analytical chemistry and = oanalytical chemistry - an unshaped social relationship2011In: Journal of the Serbian Chemical Society, ISSN 0352-5139, E-ISSN 1820-7421, Vol. 76, no 4, p. 643-646Article in journal (Refereed)
  • 127. Horvai, George
    et al.
    Worsfold, Paul
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, Jens E. T.
    European analytical column no. 39. Analytical chemistry and bioanalytical chemistry: a yet unshaped social relationship2011In: Accreditation and Quality Assurance, ISSN 0949-1775, E-ISSN 1432-0517, Vol. 16, no 4-5, p. 267-269Article in journal (Refereed)
  • 128. Hunter, Amanda L
    et al.
    Unosson, Jon
    Bosson, Jenny A
    Langrish, Jeremy P
    Pourazar, Jamshid
    Raftis, Jennifer B
    Miller, Mark R
    Lucking, Andrew J
    Boman, Christoffer
    Nyström, Robin
    Donaldson, Kenneth
    Flapan, Andrew D
    Shah, Anoop SV
    Pung, Louis
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Masala, Silvia
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sandström, Thomas
    Blomberg, Anders
    Newby, David E
    Mills, Nicholas L
    Effect of wood smoke exposure on vascular function and thrombus formation in healthy fire fighters2014In: Particle and Fibre Toxicology, ISSN 1743-8977, E-ISSN 1743-8977, Vol. 11, no 62Article in journal (Refereed)
    Abstract [en]

    Background

    Myocardial infarction is the leading cause of death in fire fighters and has been linked with exposure to air pollution and fire suppression duties. We therefore investigated the effects of wood smoke exposure on vascular vasomotor and fibrinolytic function, and thrombus formation in healthy fire fighters.

    Methods

    In a double-blind randomized cross-over study, 16 healthy male fire fighters were exposed to wood smoke (~1 mg/m3 particulate matter concentration) or filtered air for one hour during intermittent exercise. Arterial pressure and stiffness were measured before and immediately after exposure, and forearm blood flow was measured during intra-brachial infusion of endothelium-dependent and -independent vasodilators 4–6 hours after exposure. Thrombus formation was assessed using the ex vivo Badimon chamber at 2 hours, and platelet activation was measured using flow cytometry for up to 24 hours after the exposure.

    Results

    Compared to filtered air, exposure to wood smoke increased blood carboxyhaemoglobin concentrations (1.3% versus 0.8%; P < 0.001), but had no effect on arterial pressure,augmentation index or pulse wave velocity (P > 0.05 for all). Whilst there was a dose-dependent increase in forearm blood flow with each vasodilator (P < 0.01 for all), there were no differences in blood flow responses to acetylcholine, sodium nitroprusside or verapamil between exposures (P > 0.05 for all). Following exposure to wood smoke, vasodilatation tobradykinin increased (P = 0.003), but there was no effect on bradykinin-induced tissue-plasminogen activator release, thrombus area or markers of platelet activation (P > 0.05 for all).

    Conclusions

    Wood smoke exposure does not impair vascular vasomotor or fibrinolytic function, or increase thrombus formation in fire fighters. Acute cardiovascular events following firesuppression may be precipitated by exposure to other air pollutants or through other mechanisms, such as strenuous physical exertion and dehydration.

  • 129. I, Bobeldijk
    et al.
    D, Karlsson
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A, Pronk
    J, Gonsalves
    M, Hekman
    D, Van De Lagemaat
    L, Preller
    D, Heederik
    G, Skarping
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Validation of transferability of DBA derivatisation and LC-MS/MS determination method for isocyanates via an interlaboratory comparison.2008In: Ann Occup Hyg, no 52, p. 757-763Article in journal (Other (popular science, discussion, etc.))
  • 130. Idborg, H
    et al.
    Olsson, Petter
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Leclerc, P
    Raouf, J
    Jakobsson, P.J
    Korotkova, M
    Effects of mPGES-1 deletion on eicosanoid and fatty acid profiles in mice2013In: Prostaglandins & other lipid mediators, ISSN 1098-8823, E-ISSN 2212-196X, Vol. 107, p. 18-25Article in journal (Refereed)
    Abstract [en]

    mPGES-1 is considered an alternative target for anti-inflammatory treatment with improved selectivity and safety compared to NSAIDs. mPGES-1 depletion not only suppresses inflammation via absence of inducible PGE2 but might also cause an activation of anti-inflammatory pathways. We studied effects of mPGES-1 deletion on the eicosanoid and fatty acid (FA) profiles in mice. In LPS-induced peritoneal macrophages from mPGES-1 knock-out (mPGES-1−/−, KO) mice PGE2 production was markedly attenuated, whereas levels of PGD2 metabolites (15-deoxy-Δ12,14 PGJ2 and 15-deoxy-Δ12,14 PGD2) were increased compared to wild type mice. The levels of oxidized fatty acid 13-HODE were also significantly up-regulated in KO macrophages. Significant differences in the total lipid FA composition (decrease in monounsaturated FA and increase in eicosadienoic acid) were detected in spleen of KO and WT mice. These effects of mPGES-1 deletion on eicosanoid and fatty acid metabolism have important implications for future mPGES-1 inhibitors and deserve further investigation

  • 131.
    Idborg, Helena
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Analysis of Metabolites in Complex Biological Samples Using LC/MS and Multivariate Data Analysis: Metabolic Fingerprinting and Detection of Biomarkers2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To facilitate early diagnosis of diseases and elucidation of the processes involved in their development and progression, various specific compounds or ‘biomarkers’ are often monitored. The first step is to decide which compounds to analyze. An untargeted approach within the field of metabolomics, can provide a unique chemical fingerprint representing the biological state of the studied organism. Fingerprints can be used for classification and thus facilitate the identification of biomarkers and investigation of drug metabolism.

    In this work a method was developed for the general detection of metabolites using liquid chromatography/mass spectrometry (LC/MS) to obtain data for metabolic fingerprinting. One part of the project focused on generating the data and the other on analyzing the acquired data. First part: Solid phase extraction was applied to rat urine samples and protein precipitation to human plasma samples. Several LC/MS variants were used, i.e. reversed phase LC, hydrophilic interaction LC and ultrahigh pressure LC (UHPLC) coupled to a triple quadrupole MS or time of flight (ToF) MS. Second part: Methods for handling LC/MS data and extracting information, e.g. curve resolution, were evaluated. In addition data fusion methods were investigated. Principal Component Analysis (PCA) and partial least squares (PLS), were applied for pattern recognition. Furthermore, 3-way classification methods, such as parallel factor analysis (PARAFAC) and N-way PLS, were also explored.

    The developed method was applied to the early detection of phospholipi-dosis in drug development and to search for indicators of successful treatment in breast cancer therapy. Potential biomarkers were suggested, but have not yet been fully evaluated. In addition, new metabolites of an antidepressant drug were discovered and identified using this approach.

  • 132.
    Idborg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Edlund, Per-Olof
    Jacobsson, Sven P
    Multivariate approaches for efficient detection of potential metabolites from liquid chromatography/mass spectrometry data2004In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, Vol. 18, no 9, p. 944-954Article in journal (Refereed)
  • 133.
    Idborg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Edlund, Per-Olof
    Lehtiö, Janne
    Linderholm, Barbro K
    Jacobsson, Sven P
    Metabolic Fingerprinting of Human Serum Samples Shows Po-tential for Predicting Effects of Weekly Paclitaxel on Metastatic Breast Cancer – a Pilot StudyManuscript (Other academic)
  • 134.
    Idborg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Zamani, Leila
    Edlund, Per-Olof
    Schuppe-Koistinen, Ina
    Jacobsson, Sven P.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Metabolic fingerprinting of rat urine by LC/MS. Part 1. Analysis by hydrophilic interaction liquid chromatography-electrospray ionization mass spectrometry2005In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 828, no 1-2, p. 9-13Article in journal (Refereed)
  • 135.
    Idborg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Zamani, Leila
    Edlund, Per-Olof
    Schuppe-Koistinen, Ina
    Jacobsson, Sven P
    Metabolic fingerprinting of rat urine by LC/MS. Part 2. Data pretreatment methods for handling of complex data2005In: Journal of Chromatography B, ISSN 1570-0232, Vol. 828, no 1-2, p. 14-20Article in journal (Refereed)
  • 136.
    Idborg-Bjorkman, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Edlund, Per-Olof
    Kvalheim, Olav M
    Schuppe-Koistinen, Ina
    Jacobsson, Sven P
    Screening of biomarkers in rat urine using LC/electrospray ionization-MS and two-way data analysis2003In: Analytical chemistry, ISSN 0003-2700, Vol. 75, no 18, p. 4784-92Article in journal (Refereed)
  • 137.
    Isetun, Sindra
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Solid-phase Microextraction and Detection of Organophosphate Triesters in Indoor air2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the work underlying this thesis solid-phase microextraction (SPME) was evaluated as a passive sampling technique for organophosphate triesters in indoor air. These compounds are used on a large scale as flame-retarding and plastizicing additives in a variety of materials and products, and have proven to be common pollutants in indoor air. The main objective of this work was to develop an accurate method for measuring the volatile fraction. Such a method can be used in combination with active sampling to obtain information regarding the vapour/particulate distribution in different indoor environments. SPME was investigated under both equilibrium and non-equilibrium conditions and parameters associated with these different conditions were estimated.

    In Paper I, time-weighted average (TWA) SPME under dynamic conditions was investigated in order to obtain a fast air sampling method for organophosphate triesters. Among the investigated SPME coatings, the absorptive PDMS polymer had the highest affinity for the organophosphate triesters and was consequently used in all further work. Since the sampling rate is dependent on the agitation conditions, the linear airflow rates had to be carefully considered. Sampling periods as short as 1 hour were shown to be sufficient for measurements in the ng-μg m-3 range when using a PDMS 100-μm fibre and a linear flow rate above 7 cm s-1 over the fibre.

    SPME under equilibrium conditions is rather time-consuming, even under dynamic conditions, for slowly partitioning compounds such as organophosphate triesters. Nevertheless, this method has some significant advantages. For instance, the limit of detection is much lower compared to 1 h TWA sampling. Furthermore, the sampling time can be ignored as long as equilibrium has been attained. In Paper II, SPME under equilibrium conditions was investigated and evaluated for organophosphate triester vapours. Since temperature and humidity are closely associated with the distribution constant a simple study of the effect of these parameters was performed. The obtained distribution constants were used to determine the air levels in a common indoor environment. SPME and parallel active sampling on filters yielded similar results, indicating that the detected compounds were almost entirely associated with the vapour phase

    To apply dynamic SPME method in the field a sampler device, which enables controlled linear airflow rates to be applied, was constructed and evaluated (Paper III). This device was developed for application of SPME and active sampling in parallel.

    A GC/PICI-MS/MS method was developed and used in combination with active sampling of organophosphate triesters in indoor air (Paper IV). The combination of MS/MS and the soft ionization achieved with methanol as reagent gas yielded high selectivity and detection limits comparable to those provided by GC with nitrogen-phosphorus detection (NPD). The method limit of detection, when sampling 1.5 m3 of air, was in the range 0.1-1.4 ng m-3. In Paper V, the developed MS method was used in combination with SPME for indoor air measurements.

    The levels detected in the investigated indoor environments range from a few ng to μg m-3. Tris(2-chloropropyl) phosphate was detected at a concentration as high as 7 μg m-3 in a newly rebuilt lecture room.

  • 138.
    Isetun, Sindra
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Björklund, Jonas
    Nilsson, Ulrika
    Application of non-equilibrium SPME combined with GC, PICI and ion trap tandem MS for determination of airborne organophosphate flame-retardants and plasticizers in work environmentsManuscript (Other academic)
  • 139.
    Isetun, Sindra
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic field sampling of airborne organophosphate triesters using solid-phase microextraction under equilibrium and non-equilibrium conditions2005In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 30, p. 94-98Article in journal (Refereed)
    Abstract [en]

     

    A simple setup for dynamic air sampling using a solid-phase microextraction (SPME) device

    designed for use in the field was evaluated for organophosphate triester vapour under both

    equilibrium and non-equilibrium conditions. The effects of varying the applied airflows in the

    sampling device were evaluated in order to optimise the system with respect to the Reynolds

    number and magnitude of the boundary layer that developed near the surface. Further, the

    storage stability of the analytes was studied for both capped and uncapped 100-

     

     

    m

    m PDMS fibres.

    Organophosphate triesters are utilized on large scales as flame-retardants and/or plasticizers, for

    instance in upholstered furniture. In indoor working environments these compounds have become

    common components in the surrounding air. Measurements were performed in a recently

    furnished working environment and the concentration of tris(2-choropropyl) phosphate was

    found to be 7

     

     

    mg m23

    .

  • 140.
    Isetun, Sindra
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of solid-phase microextraction with PDMS for air sampling of gaseous organophosphate flame-retardants and plasticizers2004In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 380, no 2, p. 319-324Article in journal (Refereed)
    Abstract [en]

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

  • 141.
    Isetun, Sindra
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Colmsjö, Anders
    Johansson, Rolf
    Air sampling of organophosphate triesters using SPME under non-equilibrium conditions2004In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, Vol. 378, no 7, p. 1847-1853Article in journal (Refereed)
  • 142.
    J, Dahlin
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    M, Spanne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    D, Karlsson
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    M, Dalene
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    G, Skarping
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Size-separated sampling and analysis of isocyanates in workplace aerosols: Part I. Denuder-cascade impactor sampler2008In: Ann Occup Hyg, no 52, p. 361-374Article in journal (Refereed)
  • 143.
    J, Dahlin
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    M, Spanne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    M, Dalene
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    D, Karlsson
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    G, Skarping
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Size-separated sampling and analysis of isocyanates in workplace aerosols: Part II: Aging of aerosols from thermal degradation of polyurethane2008In: Ann Occu. Hyg, no 52, p. 375-383Article in journal (Refereed)
  • 144.
    Janák, Karel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Open-tubular columns for liquid and supercritical fluid chromatography1992Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Methods have been developed for the preparation of narrow-bore open tubularcolumns. In this content, condensed gases (butane, chloroethane and Freon114) were used as solvents for the static coating of these columns. Adevice for filling the narrow-bore open tubular columns with solutions incondensed gases has been designed.

    The effect of repeated cross-linking of SE-54 stationary phase, usingazo-rerr.-butane as radical initiator, on the chromatographic properties ofthe columns has been studied. Excessive repetition of the immobilizationadversely affected the chromatographic properties. Optimal conditions forthe immobilization of Carbowax 20M stationary phase using Desmodur L75 andDesmodur N75 as cross-linking reagents have been determined.

    Properties of immobilized Carbowax 20M stationary phase have beeninvestigated under LC and GC conditions at room and moderately increasedtemperatures. Glass transition temperature of the stationary phase has beenestimated. Significant changes in stationary phase selectivity anddiffusivity, dependent on the reagent applied for stationary phasecross-linking, have been found at temperatures below the glass transitiontemperature. Swelling of the immobilized stationary phase film with water -methanol mobile phases has been studied at different temperatures. Theeffect of the degree of swelling on the column retention and efficiency hasbeen estimated. Significant increase in diffusion coefficients in thestationary phase swollen with methanol at room temperature has beenobserved.

    Improvements have been made of an apparatus for measurement of diffusioncoefficients in supercritical carbon dioxide, with regard to the injection,the separation of a solute from a solvent and the back-pressure device. Anoptimization procedure has been used for the estimation of diffusioncoefficients of some test solutes.

    A selective ion-exchange stationary phase has been synthesized in situ innarrow-bore columns and, after loading with silver ions, used forargentation supercritical fluid chromatography. Good selectivity towardsunsaturated compounds has been demonstrated.

  • 145. Jarvis, Ian W. H.
    et al.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bottai, Matteo
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Stenius, Ulla
    Dreij, Kristian
    Persistent activation of DNA damage signaling in response to complex mixtures of PAHs in air particulate matter2013In: Toxicology and Applied Pharmacology, ISSN 0041-008X, E-ISSN 1096-0333, Vol. 266, no 3, p. 408-418Article in journal (Refereed)
    Abstract [en]

    Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are present in air particulate matter (PM) and have been associated with many adverse human health effects including cancer and respiratory disease. However, due to their complexity, the risk of exposure to mixtures is difficult to estimate. In the present study the effects of binary mixtures of benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP) and complex mixtures of PAHs in urban air PM extracts on DNA damage signaling was investigated. Applying a statistical model to the data we observed a more than additive response for binary mixtures of BP and DBP on activation of DNA damage signaling. Persistent activation of checkpoint kinase 1 (Chk1) was observed at significantly lower BP equivalent concentrations in air PM extracts than BP alone. Activation of DNA damage signaling was also more persistent in air PM fractions containing PAHs with more than four aromatic rings suggesting larger PAHs contribute a greater risk to human health. Altogether our data suggests that human health risk assessment based on additivity such as toxicity equivalency factor scales may significantly underestimate the risk of exposure to complex mixtures of PAHs. The data confirms our previous findings with PAH-contaminated soil (Niziolek-Kierecka et al., 2012) and suggests a possible role for Chk1 Ser317 phosphorylation as a biological marker for future analyses of complex mixtures of PAHs.

  • 146. Jarvis, I.W.H.
    et al.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Morales, D.A.
    Kummrow, F.
    Umbuzeiro, G.A.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dreij, K.
    Nanomolar levels of PAHs in extracts from urban air induce MAPK signaling in HepG2 cells2014In: Toxicology Letters, ISSN 0378-4274, E-ISSN 1879-3169, Vol. 229, no 1, p. 25-32Article in journal (Refereed)
    Abstract [en]

    Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants that occur naturally in complex mixtures. Many of the adverse health effects of PAHs including cancer are linked to the activation of intracellular stress response signaling. This study has investigated intracellular MAPK signaling in response to PAHs in extracts from urban air collected in Stockholm, Sweden and Limeira, Brazil, in comparison to BP in HepG2 cells. Nanomolar concentrations of PAHs in the extracts induced activation of MEK4 signaling with down-stream increased gene expression of several important stress response mediators. Involvement of the MEK4/JNK pathway was confirmed using siRNA and an inhibitor of JNK signaling resulting in significantly reduced MAPK signaling transactivated by the AP-1 transcription factors ATF2 and c-Jun. ATF2 was also identified as a sensitive stress responsive protein with activation observed at extract concentrations equivalent to 0.1 nM BP. We show that exposure to low levels of environmental PAH mixtures more strongly activates these signaling pathways compared to BP alone suggesting effects due to interactions. Taken together, this is the first study showing the involvement of MEK4/JNK/AP-1 pathway in regulating the intracellular stress response after exposure to nanomolar levels of PAHs in environmental mixtures.

  • 147. Jayamanne, M
    et al.
    Granelli, I
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Tjernberg, A
    Edlund, P-O
    Development of a two-dimensional liquid chromatography system for isolation of drug metabolites2010In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 51, no 3, p. 649-657Article in journal (Refereed)
    Abstract [en]

    The separation, isolation and identification of drug metabolites from complex endogenous matrices like urine, plasma and tissue extracts are challenging tasks. Metabolites are usually first identified by mass spectrometry and tentative structures proposed from product ion spectra. In many cases mass spectrometry cannot be used to determine positional isomers and metabolites have to be fractionated in microgram amounts for analysis by NMR. To overcome the difficulties associated with separation and isolation of drug metabolites from biological matrices, a new two-dimensional liquid chromatography system has been developed. The retention times of 45 acidic, basic and neutral compounds were determined on liquid chromatographic columns with different stationary phases in order to identify two columns with highly different selectivity to be used for two-dimensional liquid chromatography. Drug metabolites of three model compounds were first generated in vitro with liver microsomes and then compared with potential metabolites formed by oxidation with hydrogen peroxide catalyzed by meso-tetra (4-sulphonatophenyl) porphine (porphine). The results showed that the porphine system could be used as a complementary system for the generation of phase I microsomal metabolites with high yield of some metabolites in a less complex matrix. The two-dimensional liquid chromatography system was used to separate and isolate microsomal and porphine generated drug metabolites in off-line and on-line mode. Finally, to verify the utility of the developed system, urine samples were spiked with metabolite standards of model compounds for separation in the two-dimensional system. Excellent separations were obtained with an amide column in the first dimension and a pentafluorophenylpropyl (PFPP) column in the second dimension. The metabolites were successfully separated from each other as well as from the complex biological matrix. The results demonstrate the applicability of the system for fractionation of drug metabolites but it could also be used in many other analytical purposes, especially for basic compounds. Trace levels of metabolites were successfully separated in the on-line mode which failed in the off-line mode.

     

     

     

  • 148.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Aigret, Benoit
    De Borggraeve, Wim M.
    Spacil, Zdenek
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Selective LC-MS/MS method for the identification of BMAA from its isomers in biological samples2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 403, no 6, p. 1719-1730Article in journal (Refereed)
    Abstract [en]

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

  • 149.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Spacil, Zdenek
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. University of Washington, USA.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nilsson, Lennart
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid-Sweden University, Sweden.
    Abiotic synthesis of amino acids and self-crystallization under prebiotic conditions2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, article id 6769Article in journal (Refereed)
    Abstract [en]

    Building on previous research on the origin and homochirality of life, this study focuses on analyses profiling important building blocks of life: the natural amino acids. The spark discharge variation of the iconic Miller experiment was performed with a reducing gas mixture of ammonia, methane, water and hydrogen. Amino acid analysis using liquid chromatography coupled with tandem mass spectrometry after pre-column derivatizaiton revealed the generation of several amino acids including those essential for life. Re-crystallization of the synthetic products and enantiomeric ratio analysis were subsequently performed. Results from liquid chromatography coupled with either fluorescent detector or tandem mass spectrometry after pre-column derivatization with chiral reagent revealed spontaneous and effective asymmetric resolution of serine and alanine. This work describes a useful analytical platform for investigation of hypotheses regarding the origin and homochirality of amino acids under prebiotic conditions. The formation of numerous amino acids in the electric discharge experiment and the occurrence of high enantiomeric ratios of amino acids in re-crystallization experiment give valuable implications for future studies in unraveling fundamental questions regarding origins and evolution of life.

  • 150.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Eriksson, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lage, Sandra
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jonasson, Sara
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Shams, Shiva
    Mehine, Martin
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Rasmussen, Ulla
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Diatoms: A Novel Source for the Neurotoxin BMAA in Aquatic Environments2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 1, article id e84578Article in journal (Refereed)
    Abstract [en]

    Amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease is a neurological disorder linked to environmental exposure to a non-protein amino acid, beta-N-methylamino-L-alanine (BMAA). The only organisms reported to be BMAA-producing, are cyanobacteria - prokaryotic organisms. In this study, we demonstrate that diatoms - eukaryotic organisms - also produce BMAA. Ultra-high-performance liquid chromatography coupled with tandem mass spectrometry revealed the occurrence of BMAA in six investigated axenic diatom cultures. BMAA was also detected in planktonic field samples collected on the Swedish west coast that display an overrepresentation of diatoms relative to cyanobacteria. Given the ubiquity of diatoms in aquatic environments and their central role as primary producers and the main food items of zooplankton, the use of filter and suspension feeders as livestock fodder dramatically increases the risk of human exposure to BMAA-contaminated food.

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