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  • 1. Alves, Andreia
    et al.
    Giovanoulis, Georgios
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Swedish Environmental Research Institute, Sweden.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Erratico, Claudio
    Lucattini, Luisa
    Haug, Line S.
    Jacobs, Griet
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Leonards, Pim E. G.
    Covaci, Adrian
    Magner, Jorgen
    Voorspoels, Stefan
    Case Study on Screening Emerging Pollutants in Urine and Nails2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 7, 4046-4053 p.Article in journal (Refereed)
    Abstract [en]

    Alternative plasticizers and flame retardants (FRs) have been introduced as replacements for banned or restricted chemicals, but much is still unknown about their metabolism and occurrence in humans. We identified the metabolites formed in vitro for four alternative plasticizers (acetyltributyl citrate (ATBC), bis(2-propylheptyl) phthalate (DPHP), bis(2-ethylhexyl) terephthalate (DEHTP), bis(2ethylhexyl) adipate (DEHA)), and one FR (2,2-bis (chloromethyl)-propane-1,3-diyltetrakis(2-chloroethyl) bisphosphate (V6)). Further, these compounds and their metabolites were investigated by LC/ESI-Orbitrap-MS in urine and finger nails collected from a Norwegian cohort. Primary and secondary ATBC metabolites had detection frequencies (% DF) in finger nails ranging from 46 to 95%. V6 was identified for the first time in finger nails, suggesting that this matrix may also indicate past exposure to FRs as well as alternative plasticizers. Two isomeric forms of DEHTP primary metabolite were highly detected in urine (97% DF) and identified in finger nails, while no DPHP metabolites were detected in vivo. Primary and secondary DEHA metabolites were identified in both matrices, and the relative proportion of the secondary metabolites was higher in urine than in finger nails; the opposite was observed for the primary metabolites. As many of the metabolites present in in vitro extracts were further identified in vivo in urine and finger nail samples, this suggests that in vitro assays can reliably mimic the in vivo processes. Finger nails may be a useful noninvasive matrix for human biomonitoring of specific organic contaminants, but further validation is needed.

  • 2.
    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)
  • 3.
    Axelsson, Sara
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Eriksson, Kåre
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of resin acids during production of wood pellets-a comparison of HPLC/ESI-MS with the GC/FID MDHS 83/2 method2011In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 13, no 10, 2940-2945 p.Article in journal (Refereed)
    Abstract [en]

    Resin acids are constituents of natural and technical products of widespread use. Exposure is known to cause health effects in the airways and on the skin. Liquid chromatography/positive ion electrospray-mass spectrometry (HPLC/pos ESI-MS) was investigated for determination of 7-oxodehydroabietic (7-OXO), dehydroabietic (DHAA) and abietic acid (AA) in wood dust-containing air samples as a derivatisation-free alternative to the GC/FID HSE method 83/2, developed by the Health and Safety Executive UK. The resin acid 7-OXO was measured as a marker for oxidised resin acids, which are known to be the main contact allergens in colophonium. The found detection limits were 0.42 ng m(-3) for 7-OXO, 5.2 ng m(-3) for DHAA and 9.4 ng m(-3) for AA, respectively, which are considerably lower than with the GC/FID method (24, 115 and 89 ng m(-3)). The two methods correlated well, although consistently and significantly lower concentrations of 7-OXO were detected with LC/MS. The higher concentration of this compound with MDHS 83/2 is suggested to be an artefact from the derivatisation step in the presence of soluble wood dust remains.

  • 4.
    Carlsson, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    von Stedingk, Hans
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    LC–MS/MS Screening Strategy for Unknown Adducts to N-Terminal Valine in Hemoglobin Applied to Smokers and Nonsmokers2014In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 27, no 12, 2062-2070 p.Article in journal (Refereed)
    Abstract [en]

    Electrophilically reactive compounds have the ability to form adducts with nucleophilic sites in DNA and proteins, constituting a risk for toxic effects. Mass spectrometric detection of adducts to N-terminal valine in hemoglobin (Hb) after detachment by modified Edman degradation procedures is one approach for in vivo monitoring of exposure to electrophilic compounds/metabolites. So far, applications have been limited to one or a few selected reactive species, such as acrylamide and its metabolite glycidamide. This article presents a novel screening strategy for unknown Hb adducts to be used as a basis for an adductomic approach. The method is based on a modified Edman procedure, FIRE, specifically developed for LC-MS/MS analysis of N-terminal valine adducts in Hb detached as fluorescein thiohydantoin (FTH) derivatives. The aim is to detect and identify a priori unknown Hb adducts in human blood samples. Screening of valine adducts was performed by stepwise scanning of precursor ions in small mass increments, monitoring four fragments common for the FTH derivative of valine with different N-substitutions in the multiple-reaction mode, covering a mass range of 135 Da (m/z 503-638). Samples from six smokers and six nonsmokers were analyzed. Control experiments were performed to compare these results with known adducts and to check for artifactual formation of adducts. In all samples of smokers and nonsmokers, seven adducts were identified, of which six have previously been studied. Nineteen unknown adducts were observed, and 14 of those exhibited fragmentation patterns similar to earlier studied FTH derivatives of adducts to valine. Identification of the unknown adducts will be the focus of future work. The presented methodology is a promising screening tool using Hb adducts to indicate exposure to potentially toxic electrophilic compounds and metabolites.

  • 5.
    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, 2517-2529 p.Article 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.

  • 6.
    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, 112-119 p.Article 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.

  • 7.
    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.

  • 8.
    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, 633-638 p.Article 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.

  • 9.
    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, 1309-1314 p.Article 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.

  • 10.
    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, 94-98 p.Article 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

    .

  • 11.
    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, 319-324 p.Article 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.

  • 12.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Strategy for quantifying trace levels of BMAA in cyanobacteria by LC/MS/MS2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 4, 1283-1292 p.Article in journal (Refereed)
    Abstract [en]

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

  • 13. Johansson, Staffan
    et al.
    Redeby, Theres
    Altamore, Timothy M.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Börje, Anna
    Mechanistic Proposal for the Formation of Specific Immunogenic Complexes via a Radical Pathway: A Key Step in Allergic Contact Dermatitis to Olefinic Hydroperoxides2009In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 22, no 11, 1774-1781 p.Article in journal (Refereed)
    Abstract [en]

    The widespread use of scented products causes an increase of allergic contact dermatitis to fragrance compounds in Western countries today. Many fragrance compounds are prone to autoxidation, forming hydroperoxides as their primary oxidation products. Hydroperoxides are known to be strong allergens and to form specific immunogenic complexes. However, the mechanisms for the formation of the immunogenic complexes are largely unknown. We have investigated this mechanism for (5R)-5-isopropenyl-2-methyl-2-cyclohexene-1-hydroperoxide (Lim-2-OOH) by studying the formation of adducts in the reaction between this hydroperoxide and 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)TPPCl) in the presence of protected cysteine (NAc-Cys-OMe) or glutathione (GSH). Isolated adducts originate from the addition of the thiol group of NAc-Cys-OMe over the carbon−carbon double bonds of carvone. Furthermore, adducts between NAc-Cys-OMe and carveol as well as between GSH and carvone have been identified. The formation of these adducts most likely proceeds via the radical thiol−ene mechanism. The addition of a terpene moiety to cysteine offers an explanation of the specificity of the immune response to structurally different hydroperoxides. These results also explain the lack of cross-reactivity between carvone and Lim-2-OOH. In conclusion, we propose that immunogenic complexes of olefinic hydroperoxides can be formed via the radical thiol−ene mechanism. These complexes will be specific for the individual olefinic hydroperoxides due to the inclusion of a terpene moiety derived from the hydroperoxide.

  • 14.
    Karlsson, Isabella
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Samuelsson, Kristin
    Ponting, David J.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Peptide Reactivity of Isothiocyanates - Implications for Skin Allergy2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, 21203Article in journal (Refereed)
    Abstract [en]

    Skin allergy is a chronic condition that affects about 20% of the population of the western world. This disease is caused by small reactive compounds, haptens, able to penetrate into the epidermis and modify endogenous proteins, thereby triggering an immunogenic reaction. Phenyl isothiocyanate (PITC) and ethyl isothiocyanate (EITC) have been suggested to be responsible for allergic skin reactions to chloroprene rubber, the main constituent of wetsuits, orthopedic braces, and many types of sports gear. In the present work we have studied the reactivity of the isothiocyanates PITC, EITC, and tetramethylrhodamine-6-isothiocyanate (6-TRITC) toward peptides under aqueous conditions at physiological pH to gain information about the types of immunogenic complexes these compounds may form in the skin. We found that all three compounds reacted quickly with cysteine moieties. For PITC and 6-TRITC the cysteine adducts decomposed over time, while stable adducts with lysine were formed. These experimental findings were verified by DFT calculations. Our results may suggest that the latter are responsible for allergic reactions to isothiocyanates. The initial adduct formation with cysteine residues may still be of great importance as it prevents hydrolysis and facilitates the transport of isothiocyanates into epidermis where they can form stable immunogenic complexes with lysine-containing proteins.

  • 15.
    Keshavarzi, Neda
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Mace, Amber
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ansari, Farhan
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Berglund, Lars
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanocellulose-Zeolite Composite Films for Odor EliminationManuscript (preprint) (Other academic)
    Abstract [en]

    Free standing and strong odor-removing composite films of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite adsorbents have been produced by colloidal processing. Thermogravimetric desorption analysis (TGA) and infrared spectroscopy combined with computational simulations showed that three commercially available zeolites- silicalite, ZSM5 and zeolite Y, have a high affinity and uptake of important odors like ethanethiol and propanethiol, also in the presence of water. Highly flexible and strong free standing zeolite-CNF films with a thickness up to 115 μm and an adsorbent loading above 80 w/w% were obtained by gelation and vacuum filtration. Zeolite-CNF films displayed high mechanical strength of up to 10 MPa. Headspace solid phase microextraction (SPME) coupled to gas chromatography- mass spectroscopy (GC-MS) analysis showed that the CNF-zeolite films can eliminate volatile thiol-based odors to concentrations below the detection ability of the human olfactory system. The odor-removing performance of the zeolite-cellulose nanofibril films could enable improved transport and storage of fruits and vegetables rich in odors, e.g. onion and the tasty but foul-smelling South-East Asian Durian fruit.

  • 16.
    Keshavarzi, Neda
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Rad, Farshid Mashayekhy
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mace, Amber
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ansari, Farhan
    Akhtar, Farid
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Berglund, Lars
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanocellulose-Zeolite Composite Films for Odor Elimination2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 26, 14254-14262 p.Article in journal (Refereed)
    Abstract [en]

    Free standing and strong odor-removing composite films of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite adsorbents have been colloidally processed. Thermogravimetric desorption analysis (TGA) and infrared spectroscopy combined with computational simulations showed that commercially available silicalite-1 and ZSM-5 have a high affinity and uptake of volatile odors like ethanethiol and propanethiol, also in the presence of water. The simulations showed that propanethiol has a higher affinity, up to 16%, to the two zeolites compared with ethanethiol. Highly flexible and strong free-standing zeolite CNF films with an adsorbent loading of 89 w/w% have been produced by Ca-induced gelation and vacuum filtration. The CNF-network controls the strength of the composite films and 100 mu m thick zeolite CNF films with a CNF content of less than 10 vol % displayed a tensile strength approaching 10 MPa. Headspace solid phase microextraction (SPME) coupled to gas chromatography mass spectroscopy (GC/MS) analysis showed that the CNF zeolite films can eliminate the volatile thiol-based odors to concentrations below the detection ability of the human olfactory system. Odor removing zeolite-cellulose nanofibril films could enable improved transport and storage of fruits and vegetables rich in odors, for example, onion and the tasty but foul-smelling South-East Asian Durian fruit.

  • 17.
    Leck, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gao, Qiuju
    Stockholm University, Faculty of Science, Department of Meteorology .
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Meteorology . Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Size-resolved atmospheric particulate polysaccharides in the high summer Arctic2013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 24, 12573-12588 p.Article in journal (Refereed)
    Abstract [en]

    Size-resolved aerosol samples for subsequent quantitative determination of polymer sugars (polysaccharides) after hydrolysis to their subunit monomers (monosaccharides) were collected in surface air over the central Arctic Ocean during the biologically most active summer period. The analysis was carried out by novel use of liquid chromatography coupled with highly selective and sensitive tandem mass spectrometry. Polysaccharides were detected in particle sizes ranging from 0.035 to 10 mu m in diameter with distinct features of heteropolysaccharides, enriched in xylose, glucose + mannose as well as a substantial fraction of deoxysugars. Polysaccharides, containing deoxysugar monomers, showed a bimodal size structure with about 70% of their mass found in the Aitken mode over the pack ice area. Pentose (xylose) and hexose (glucose + mannose) had a weaker bimodal character and were largely found with super-micrometer sizes and in addition with a minor sub-micrometer fraction. The concentration of total hydrolysable neutral sugars (THNS) in the samples collected varied over two orders of magnitude (1 to 160 pmol m(-3)) in the supermicrometer size fraction and to a somewhat lesser extent in sub-micrometer particles (4 to 140 pmol m(-3)). Lowest THNS concentrations were observed in air masses that had spent more than five days over the pack ice. Within the pack ice area, about 53% of the mass of hydrolyzed polysaccharides was detected in sub-micrometer particles. The relative abundance of sub-micrometer hydrolyzed polysaccharides could be related to the length of time that the air mass spent over pack ice, with the highest fraction (> 90 %) observed for > 7 days of advection. The aerosol samples collected onboard ship showed similar monosaccharide composition, compared to particles generated experimentally in situ at the expedition's open lead site. This supports the existence of a primary particle source of polysaccharide containing polymer gels from open leads by bubble bursting at the air-sea interface. We speculate that the occurrence of atmospheric surface-active polymer gels with their hydrophilic and hydrophobic segments, promoting cloud droplet activation, could play a potential role as cloud condensation nuclei in the pristine high Arctic.

  • 18.
    Leck, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Qiuju, Gao
    Stockholm University, Faculty of Science, Department of Meteorology .
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Size-resolved polysaccharides in summer high Arctic aerosol relevant to cloud formation.Manuscript (preprint) (Other academic)
  • 19.
    Maddalo, Gianluca
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Adams, Christopher M.
    Fung, Eva
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Zubarev, Roman A.
    Sedzik, Jan
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Porcine P2 myelin protein primary structure and bound fatty acids determined by mass spectrometry2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 397, no 5, 1903-1910 p.Article in journal (Refereed)
    Abstract [en]

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

  • 20. Möller, Kristina
    et al.
    Davies, Ronnie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fred, Charlotta
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of molecularly imprinted solid-phase extraction for a 1,2:3,4-diepoxybutane adduct to valine in haemoglobin2010In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 878, no 27, 2497-2501 p.Article in journal (Refereed)
    Abstract [en]

    A molecularly imprinted polymer, MIP, was prepared and evaluated as SPE sorbent for a cyclicized adduct formed to N-terminal valine (Pyr-Val) in hemoglobin from 1,2:3,4-diepoxybutane (DEB). This metabolite plays an important role in the carcinogenesis of 1,3-butadiene. The hydrazide of Pyr-Val, formed after hydrazinolysis of hemoglobin, as well as necessary standards was synthesized. The MIP was prepared from methacrylic acid with a structure analogue to the investigated adduct as template and the method was developed for aqueous conditions. Selective desorption was achieved when the sample was washed with water after loading in 10% acetonitrile. The primary interaction with the binding sites in the imprints was most likely of ionic character. Quantification of the Pyr-Val adduct was performed with LC/ESI-MS/MS, yielding an instrumental LOD of 150 pg injected amount.

  • 21. Natsch, Andreas
    et al.
    Gunthardt, Barbara F.
    Corbi, Elise
    Peres, Christophe
    Dusterloh, Andre
    Leijs, Hans
    van Strien, Michel
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Calandra, Michael J.
    Wang, Ying
    Interlaboratory evaluation of methods to quantify skin sensitizing hydroperoxides potentially formed from linalool and limonene in perfumes2017In: Flavour and fragrance journal, ISSN 0882-5734, E-ISSN 1099-1026, Vol. 32, no 4, 277-285 p.Article in journal (Refereed)
    Abstract [en]

    The fragrant terpenes limonene and linalool can form skin sensitizing hydroperoxides upon prolonged exposure to air. Recently, high frequencies of positive patch tests to oxidized linalool and limonene were reported from multiple dermatological centres. However, there is a lack of data indicating potential sources of consumer exposure to sensitizing doses of terpene hydroperoxides which explains this frequent contact allergy. Within the IDEA project ( International Dialogue for the Evaluation of Allergens; http://ideaproject.info/), a taskforce was formed to drive analytical method development and evaluation. In an inter-laboratory study in five laboratories, a method based on hydroperoxide reduction combined with GC-MS was tested for reproducibility. Blinded samples of commercial fine fragrances were spiked with four different hydroperoxides. In samples spiked with 100-200 mu g/ml, an average recovery of 86-105% with a relative standard deviation between laboratories of 7.4-22% was found. In samples spiked with 2050 mu g/ml, the recovery was 85-91%. The reduction approach offers a transferable and reproducible method to indirectly detect low levels of hydroperoxides, at least in fine fragrances. Ideally, one would prefer to directly detect the parent hydroperoxide. Therefore the same samples were further tested with three LC-based methods directly detecting the parent hydroperoxide. LC coupled to chemiluminescence, LC-Q-TOF-MS or LC-orbitrap-MS were used. Results indicate that with specific gradients a separation of the four analytes and quantification in the fragrance matrix can be achieved. Results of this method evaluation study present a toolbox of methods to detect terpene hydroperoxides to further investigate consumer exposure.

  • 22.
    Nilsson, Ulrika
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Ann-Therese
    Lassen, Pia
    Development and validation of a method for the analysis of colophonium in cosmetic products: Rapport till Dansk Miljöstyrelse, Dec 07. Dansk Miljöundersögelser2007Report (Other academic)
  • 23.
    Nilsson, Ulrika Nilsson
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Berglund, Naghmeh
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Lindahl, F
    Axelsson, Sara
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Redeby, Theres
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    SPE and HPLC/UV of resin acids in colophonium-containing products2008In: Journal of Separation Science, Vol. 31, no 15, 2784-2790 p.Article in journal (Refereed)
    Abstract [en]

    A new method, involving SPE and HPLC/UV diode-array detection (DAD), was developed for the quantification of colophonium components in different consumer products, such as cosmetics. Colophonium is a common cause of contact dermatitis since its components can oxidize into allergens on exposure to air. Three different resin acids were used as markers for native and oxidized colophonium, abietic acid (AbA), dehydroabietic acid (DeA), and 7-oxodehydroabietic acid (7-O-DeA). The SPE method, utilizing a mixed-mode hydrophobic and anion exchange retention mechanism, was shown to yield very clean extracts. The use of a urea-embedded C12 HPLC stationary phase improved the separation of the resin acids compared to common C18. Concentrations higher than 2 mg/g of both AbA and DeA were detected in wax strips. In this product also 7-O-DeA, a marker for oxidized colophonium, was detected at a level of 28 μg/g. The LODs were in the range of 7–19 μg/g and the LOQs 22–56 μg/g. The method is simple to use and can be applied on many types of technical products, not only cosmetics. For the first time, a method for technical products was developed, which separates AbA from pimaric acid

  • 24.
    Nordqvist, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Melin, Jens
    Nilsson, Ulrika
    Johansson, Rolf
    Colmsjö, Anders
    Comparison of denuder and impinger sampling for determination of gaseous toluene diisocyanate (TDI)2001In: Fresenius´ Journal of Analytical Chemistry, ISSN 0937-0633, Vol. 371, no 1, 39-43 p.Article in journal (Refereed)
    Abstract [en]

     

    An air-sampling method employing denuders coated inside with a chemisorptive stationary phase has been evaluated for analysis of the hazardous gaseous 2,4 and 2,6 isomers of toluene diisocyanate (TDI). The denuder stationary phase consisted of polydimethylsiloxane (SE-30) to which dibutylamine (DBA) was added as a reagent for derivatization of TDI. The accuracy and precision of sampling by means of denuders were shown to differ only slightly from those of the established impinger method. The denuder method was, however, also shown to be suitable for long-term measurements (up to 8 h). The limit of determination (LOD) of the method, including LC-APCI-MS-MS analysis, was found to be 1.9 µg m-3 and 1.2 µg m-3 for 2,4- and 2,6-TDI, respectively, for short-term measurements (15 min). Significant lower LOD was obtained for long-term measurements.This is well below the Occupational Safety and Health Administration (OSHA) 8-h TWA (time weighted average) exposure limit, which is 40 µg m-3 for the sum of the TDI isomers. The denuder method was also found to be robust and easy to handle. The samplers can be prepared several days before sampling with no loss in performance. The contents of denuders should, on the other hand, be extracted immediately after sampling to prevent degradation of the isocyanate derivatives formed.

     

  • 25.
    Nordqvist, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Colmsjö, Anders
    Evaluation of denuder sampling for a mixture of three common gaseous diisocyanates2003In: Analytical and bioanalytical chemistry, ISSN 1618-2642, Vol. 375, no 6, 786-791 p.Article in journal (Refereed)
    Abstract [en]

    A denuder sampler has been evaluated for a mixture of three gaseous diisocyanates, i.e. toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Sampling was performed at a total concentration of diisocyanates close to the Swedish occupational exposure limit (OEL), which is 10 ppbv (69–92 µg m–3), for a 5-min period. The denuder tube was coated with a chemosorptive stationary phase consisting of SE-30 (polydimethylsiloxane) and the derivatising reagent dibutylamine (DBA). It was shown that the denuder has a collection efficiency for HDI and IPDI comparable to that of an impinger method, while sampling of TDI resulted in an 8% lower concentration. Both short-term (15 min) and long-term (8 h) sampling periods were shown to yield reproducible results. For 8-h measurements, a sampling flow rate of 5 mL min–1 was shown to be suitable for the investigated concentration range, i.e. 10–100 ppbv (69–921 µg m–3). A flow rate of 25 mL min–1 or higher resulted in breakthrough after 8 h due to chromatography of the compounds in the adsorbent. The limit of detection (LOD) for the air sampling method is nearly 500 times lower than the OEL. The denuder tubes can be prepared at least 10 days prior to sampling without degradation of performance. Furthermore, they can be stored up to 6 days in a freezer after sampling without significant loss of analytes.

  • 26.
    Nordqvist, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Investigation of a cylindrical chemosorptive denuder for sampling and phase separation of toluene diisocyanate aerosols.2005In: Anal Bioanal Chem, ISSN 1618-2642, Vol. 382, no 5, 1294-9 p.Article in journal (Other academic)
  • 27.
    Nordqvist, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Colmsjö, Anders
    Investigation of a cylindrical chemosorptive denuder for sampling and phase separation of toluene diisocyanate aerosols2005In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 382, no 5, 1294-1299 p.Article in journal (Refereed)
    Abstract [en]

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

  • 28.
    Nordqvist, Yvonne
    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.
    Dahl, Andreas
    Gudmundsson, Anders
    Evaluation of a cylindrical denuder designed for personal exposure measurements of methylene diphenyl diisocyanate aerosolsManuscript (preprint) (Other (popular science, discussion, etc.))
  • 29.
    Olsson, Petter
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Holmbäck, Jan
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Herslöf, Bengt
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Separation And Identification Of Lipid Classes By Normal Phase Lc-Esi/Ms/Ms On A Cyanopropyl Column2014In: European Journal of Lipid Science and Technology, ISSN 1438-7697, E-ISSN 1438-9312, Vol. 116, no 5, 653-658 p.Article in journal (Refereed)
    Abstract [en]

    In order to establish a versatile and convenient method for the analysis of lipids, electrospray ionization tandem mass spectrometry (ESI-MS/MS) was applied to a HPLC separation on a cyanopropyl-bonded stationary phase. A binary gradient mobile phase system consisting of hexane, toluene, methanol and a stable electrospray yielding sodium adduct ions could be used to generate specific product ions in MS/MS mode. By applying the LC/ESI-MS/MS method on an egg yolk sample, 29 different molecular species of phosphatidylethanolamines, phosphatidylcholines, and lysophosphatidylcholines could be detected within 25 min.

  • 30. Raison-Peyron, Nadia
    et al.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Du-Thanh, Aurélie
    Karlberg, Ann-Therese
    Widespread contact dermatitis from unexpected exposure to rosin from a toilet seat2013In: Dermatitis, ISSN 1710-3568, E-ISSN 2162-5220, Vol. 24, no 3, 149-150 p.Article in journal (Refereed)
  • 31.
    Ramzy, Ahmad G.
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hagvall, Lina
    Pei, Mansoureh N.
    Samuelsson, Kristin
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Investigation of diethylthiourea and ethyl isothiocyanate as potent skin allergens in chloroprene rubber2015In: Contact Dermatitis, ISSN 0105-1873, E-ISSN 1600-0536, Vol. 72, no 3, 139-146 p.Article in journal (Refereed)
    Abstract [en]

    Background

    Exposure to chloroprene rubber has resulted in numerous cases of allergic contact dermatitis, attributed to organic thiourea compounds used as vulcanization accelerators. However, thiourea compounds are not considered to be strong haptens.

    Objectives

    To analyse common commercial chloroprene materials for their contents of diethylthiourea (DETU), dibutylthiourea (DBTU), diphenylthiourea (DPTU), and their degradation products, isothiocyanates; and to investigate the sensitization potencies of possible degradation products of the mentioned thiourea compounds.

    Methods

    Liquid chromatography/mass spectrometry (MS) was used for quantification of organic thiourea compounds in chloroprene products, such as medical, sports and diving gear; isothiocyanates were measured by solid-phase microextraction/gas chromatography/MS. Sensitization potencies were determined with the murine local lymph node assay (LLNA).

    Results

    DETU was identified at concentrations of 2.7-9.4 mu g/cm(2) in all samples, whereas neither DBTU nor DPTU was detected. At 37 degrees C, degradation of DETU in the materials to ethyl isothiocyanate (EITC) was detected. EITC and ethyl isocyanate showed extreme and strong sensitization potencies, respectively, in the LLNA.

    Conclusions

    DETU can act as a prehapten, being degraded to EITC when subjected to body temperature upon skin contact. EITC could thus be the culprit behind allergic contact dermatitis caused by chloroprene rubber.

  • 32.
    Ramzy, Ahmad G.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Lammintausta, K.
    Matura, M.
    Bråred Christensson, J.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Hagvall, L.
    Isothiocyanates are important as haptens in contact allergy to chloroprene rubber2017In: British Journal of Dermatology, ISSN 0007-0963, E-ISSN 1365-2133, Vol. 177, no 2, 522-530 p.Article in journal (Refereed)
    Abstract [en]

    Background Contact allergy to chloroprene rubber products is well known. Thiourea compounds are considered the cause of allergy. Diethylthiourea commonly occurs in this type of product and can decompose to the sensitizer ethyl isothiocyanate. Objectives To investigate the clinical importance of degradation products and metabolites from organic thioureas in contact allergy to chloroprene rubber with a focus on isothiocyanates and isocyanates. Methods Patients with contact allergy to diphenylthiourea were patch tested with phenyl isothiocyanate and phenyl isocyanate. Patients with known contact allergy to diethylthiourea were retested with diethylthiourea, while chemical analyses of their chloroprene rubber products were performed. The stability of diethylthiourea, diphenylthiourea and dibutylthiourea in patch-test preparations was investigated. Liquid chromatography/mass spectrometry and solid-phase microextraction/gas chromatography were used for determination of organic thioureas and isothiocyanates. Results All patients allergic to diphenylthiourea reacted to phenyl isothiocyanate, two of eight reacted to phenyl isocyanate and six of eight reacted to diphenylthiourea. Four patients allergic to diethylthiourea reacted at retest; diethylthiourea was detected in all chloroprene rubber samples, with levels of 2-1200 nmol cm(-2). At 35 degrees C, ethyl isothiocyanate was emitted from all samples. Patch-test preparations of diethylthiourea, diphenylthiourea and dibutylthiourea all emitted the corresponding isothiocyanate, with diethylthiourea showing the highest rate of isothiocyanate emission. Conclusions Thiourea compounds are degraded to isothiocyanates, which are generally strong or extreme sensitizers, thus acting as prehaptens. This process occurs in both chloroprene rubber products and patch-test preparations. Positive reactions to phenyl isocyanate indicate cutaneous metabolism, as the only known source of exposure to phenyl isocyanate is through bioactivation of diphenylthiourea.

  • 33.
    Redeby, Theres
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Altamore, Timothy A.
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ambrosi, Annalisa
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Broo, Kerstein
    Borje, Anna
    Karlberg, Ann-Therese
    Specific Adducts Formed through a Radical Reaction between Peptides and Contact Allergenic Hydroperoxides2010In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 23, no 1, 203-210 p.Article in journal (Refereed)
    Abstract [en]

    The first step in the development of contact allergy (allergic contact dermatitis) includes the penetration of an allergy-causing chemical (hapten) into the skin, where it binds to macromolecules such as proteins. The protein-hapten adduct is then recognized by the immune system as foreign to the body. For hydroperoxides, no relevant hapten target proteins or protein-hapten adducts have so far been identified. In this work, bovine insulin and human angiotensin I were used as model peptides to investigate the haptenation mechanism of three hydroperoxide haptens: (5R)-5-isopropenyl-2-methyl-2-cyclohexene-1-hydroperoxide (Lim-2-OOH), cumene hydroperoxide (CumOOH), and 1-(1-hydroperoxy-1-methylethyl) cyclohexene (CycHexOOH). These hydroperoxides are expected to react via a radical mechanism, for which 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)TPPCl) was used as a radical initiator. The reactions were carried out in 1:1 ethanol/10 mM amonium acetate buffer pH 7.4, for 3 h at 37 T, and the reaction products were either enzymatically digested or analyzed directly by MALDI/TOF-MS, HPLC/MS/MS, and 2D gel electrophoresis. Both hydroperoxide-specific and unspecific reaction products were detected, but only it) the presence of the iron catalyst. In the absence of catalyst, the hydroperoxides remained unreacted. This suggests that the hydroperoxides call enter into the skin and remain inert until activated. Through the detection of a Lim-2-OOH adduct bound at the first histidine (of two) of angiotensin I, it was confirmed that hydroperoxides have the potential to form specific antigens in contact allergy.

  • 34. Rudback, Johanna
    et al.
    Bergstrom, Moa Andresen
    Borje, Anna
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Ann-Therese
    alpha-Terpinene, an Antioxidant in Tea Tree Oil, Autoxidizes Rapidly to Skin Allergens on Air Exposure2012In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 25, no 3, 713-721 p.Article in journal (Refereed)
    Abstract [en]

    The monoterpene alpha-terpinene is used as a fragrance compound and is present in different essential oils. It is one of the components responsible for the antioxidant activity of tea tree oil. alpha-Terpinene is structurally similar to other monoterpenes, e.g., limonene, known to autoxidize on air exposure and form allergenic compounds. The aim of the present study was to investigate the possible autoxidation of alpha-terpinene at room temperature. To investigate the sensitization potency of air-exposed alpha-terpinene and the oxidation products formed, the murine local lymph node assay was used. Chemical analysis showed that alpha-terpinene degrades rapidly, forming allylic epoxides and p-cymene as the major oxidation products and also hydrogen peroxide. Thus, the oxidation pathway differs compared to that of, e.g., limonene, which forms highly allergenic hydroperoxides as the primary oxidation products on autoxidation. The sensitization potency of alpha-terpinene was increased after air-exposure. The allylic epoxides and a fraction, in which only an alpha,beta-unsaturated aldehyde could be identified, were shown to be strong sensitizers in the local lymph node assay. Thus, we consider them to be the major contributors to the increased sensitization potency of the autoxidized mixture. We also investigated the presence of alpha-terpinene and its oxidation products in four different tea tree oil samples of various ages. alpha-Terpinene and its oxidation products were identified in all of the tea tree oil samples. Thus, from a technical perspective, alpha-terpinene is a true antioxidant since it autoxidizes rapidly compared with many other compounds, preventing these from degradation. However, as it easily autoxidizes to form allergens, its suitability can be questioned when used in products for topical applications, e.g., in tea tree oil but also in cosmetics and skin care products.

  • 35. Rudback, Johanna
    et al.
    Ramzy, Ahmed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Ann-Therese
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of allergenic hydroperoxides in essential oils using gas chromatography with electron ionization mass spectrometry2014In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 37, no 8, 982-989 p.Article in journal (Refereed)
    Abstract [en]

    Fragrance monoterpenes are widely used commercially due to their pleasant scent. In previous studies, we have shown that air-exposed monoterpenes form hydroperoxides that are strong skin sensitizers. Methods for detection and quantification of the hydroperoxides in essential oils and scented products are thus desirable. Due to thermolability and low UV absorbance, this is a complicated task. We have recently developed a sensitive LC-ESI-MS method, but with limited structural information and separation efficiency for positional isomers and stereoisomers. In the present study, we investigated derivatization with a trimethyl silyl reagent and subsequent GC with electron ionization MS for the determination of monoterpene hydroperoxides. All investigated monoterpene hydroperoxides could be chromatographed as thermostable trimethyl silyl derivatives and yielded the fragment m/z 89 ([OSi(CH3)(3)](+)) at a higher extent compared to corresponding alcohols. Limonene-2-hydroperoxide and four other hydroperoxide isomers of limonene were separated and detected in sweet orange oil autoxidized for two months. The concentration of limonene-2-hydroperoxide isomers was found to be 19 g/mg in total. Also isomers of linalyl acetate hydroperoxide and linalool hydroperoxide were detected in autoxidized petitgrain oil (two months). The presented GC-MS method showed concentrations in the same order as previous LC-MS/MS analysis of the same type of oils.

  • 36. Rudbäck, Johanna
    et al.
    Hagvall, Lina
    Börje, Anna
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Ann-Therese
    Characterization of skin sensitizers from autoxidized citronellol - impact of the terpene structure on the autoxidation process2014In: Contact Dermatitis, ISSN 0105-1873, E-ISSN 1600-0536, Vol. 70, no 6, 329-339 p.Article in journal (Refereed)
    Abstract [en]

    Background. Citronellol is a frequently used fragrance compound in consumer products. It is present in fragrance mix II, which is used for screening of contact allergy to fragrances. Because of its chemical structure, citronellol could be susceptible to autoxidation. Objectives. To compare the behaviour of citronellol with that of the structurally similar compounds linalool and geraniol, in terms of ability to autoxidize, the products formed, and the sensitization potencies of these. Methods. Citronellol was exposed to air, and autoxidation was followed by gas chromatography-mass spectrometry (GC-MS) analysis after derivatization of thermolabile compounds. The sensitizing potencies of the oxidation mixture and its major oxidation compounds were examined with the local lymph node assay. Results. The concentration of citronellol decreased while the sensitization potency increased in air-exposed samples over time, with hydroperoxides being identified as the major oxidation products and main skin sensitizers. Conclusions. The present study shows the impact of the absence of the 2,3-double bond in the citronellol structure on the oxidation pathways for formation of oxidation products. The study also shows the usefulness of our new GC-MS method for quantification of the citronellol oxidation products, especially the hydroperoxides. The investigated citronellol hydroperoxides could be important allergens, owing to the high concentrations detected and frequent exposure to citronellol in the population.

  • 37. Rudbäck, Johanna
    et al.
    Islam, Nurul
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Ann-Therese
    A sensitive method for determination of allergenic fragrance terpene hydroperoxides using liquid chromatography coupled with tandem mass spectrometry2013In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 36, no 8, 1370-1378 p.Article in journal (Refereed)
    Abstract [en]

    Different compositions of monoterpenes are utilized for their pleasant scent in cosmetics and perfumes. However, the most commonly used fragrance terpenes easily oxidize upon contact with air, forming strongly skin-sensitizing hydroperoxides. Due to their thermolability and low UV absorbance, detection methods for hydroperoxides are scarce. For the first time, a simple and sensitive method using LC/ESI-MS/MS was developed to quantitatively determine hydroperoxides from the common fragrance compounds linalool, linalyl acetate, and limonene. The method was applied to autoxidized petitgrain oil and sweet orange oil. A separation was accomplished using a C3 column. The method LOD for the investigated hydroperoxides in the essential oils was below 0.3 g/mL, corresponding to 0.3 ppm. For prevention purposes and according to EU regulations, concentrations in cosmetics exceeding 100 ppm in rinse-off and 10 ppm in stay-on products of linalool and limonene must be labeled. However, the products may still contain allergens, such as hydroperoxides, formed by oxidative degradation of their parent terpenes. The sensitivity and selectivity of the presented LC/MS/MS method enables detection of hydroperoxides from the fragrance terpenes linalool, linalyl acetate, and limonene. However, for routine measurements, the method requires further validation.

  • 38.
    Tollbäck, Johanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Isetun, Sindra
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic non-equilibrium SPME combined with GC, PICI, and ion trap MS for determination of organophosphate esters in air2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 396, no 2, 839-844 p.Article in journal (Refereed)
    Abstract [en]

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

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