Change search
Refine search result
2345678 201 - 250 of 370
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 201.
    Marand, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dahlin, Jakob
    Karlsson, Daniel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dalene, Marianne
    Determination of technical grade isocyanates used in the production of polyurethane plastics2004In: Journal of Environmental Monitoring, Vol. 6, no 7, p. 606-614Article in journal (Refereed)
    Abstract [en]

    A method for determination of technical grade isocyanates used in the production of polyurethane (PUR) is presented. The isocyanates in technical grade products were characterised as di-n-butylamine (DBA) derivatives using LC-MS and LC-chemiluminescent nitrogen detection (CLND) and the total isocyanate content was compared to a titration assay. For collection of isocyanates in air, an impinger–filter sampling technique with DBA as derivatisation reagent was used. Characterised DBA and nonadeuterium labelled DBA derivatives of isocyanates in technical products were used as calibration standards and internal standards, respectively, in the analysis of air samples. Three workplaces were studied where PUR products were produced either by spraying or by moulding. In both technical products and in air samples, a number of monomeric, oligomeric and prepolymeric isocyanates of e.g. methylenebisphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI) were characterised. Several of these have not previously been described in workplace atmospheres. In the technical isocyanate products, between 69 and 102% of the NCO content determined by titration was accounted for by LC-CLND. Quantifications of a wide range of isocyanates in air samples were performed with correlation coefficients in the range 0.988–0.999 (n= 8) and the instrumental detection limits were 0.7–25 pg. At the two workplaces where MDI- and HDI isocyanurate-based products were sprayed, the isocyanate composition in the air reflected the composition in the technical product. At the workplace where a MDI-based product was used in a moulding process, only the monomeric isocyanates were found in the air. The advantage of using characterised technical grade isocyanates as analytical standards was clearly demonstrated and the possibility of using index compounds when monitoring isocyanate exposure is discussed.

  • 202.
    Marand, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Dalene, Marianne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of amines as pentafluoropropionic acid anhydride derivatives in biological samples using liquid chromatography and tandem mass spectrometry2004In: The Analyst, ISSN 0003-2654, Vol. 129, no 6, p. 522-528Article in journal (Refereed)
    Abstract [en]

    Determination of amines in biological samples as markers of exposure to the amines or the corresponding isocyanates is an important tool for industrial exposure assessment. In this study, a liquid chromatography and tandem mass spectrometry (LC- MS/ MS) method for determination of amines in biological samples as perfluorofatty amides derivatives is presented. The method enables determination of diamines such as methylene diamine (MDA), toluene diamine (TDA), naphthalene diamine (NDA), hexamethylene diamine (HDA), isophorone diamine (IPDA), methylenedi( cyclohexylamine) (HMDA) and 4,4'-methylene-(2-chloroaniline) (MOCA) in human urine and plasma. The work-up procedure included hydrolysis of the biological samples with 3 M H2SO4 at 100degreesC for 16 h and extraction of the amines into toluene, where derivatisation of the amines with perfluorofatty acid anhydride was performed. Following removal of excess reagent and the acid formed and an exchange of solvent, the derivatives were analysed using gradient elution with an acetonitrile/water mobile phase composition and electrospray ionisation (ESI) with multiple reaction monitoring (MRM) of [M - H](-) --> [M - H - 120](-) or [119](-). Several perfluorofatty acid anhydrides were evaluated as derivatisation reagents, but the LC chromatographic properties of the pentafluoropropionic acid anhydride (PFPA) derivatives were favourable. Quantification of amine - PFPA derivatives was performed using deuterium labelled amine - PFPA derivatives as internals standards with good precision and linearity in the investigated range of 0 - 20 ng ml(-1) urine. The instrumental detection limits for the amine - PFPA derivatives were 0.2 - 3 fmol for MRM of [M - H](-) --> [119](-) and 0.3 - 8 fmol for [M - H](-) --> [M - H - 120](-). In 10 urine and 6 plasma samples from workers exposed to isocyanates, determination of TDA and MDA as PFPA derivatives was performed using LC- MS/ MS and a reference GC-MS method. No significant difference between the two methods was observed.

  • 203.
    Marand, Åsa
    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.
    Extractable organic compounds in polyurethane foam with special reference to aromatic amines and derivatives thereof2004In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 510, no 1, p. 109-119Article in journal (Refereed)
    Abstract [en]

    Methods for determination of aromatic amines and related compounds in flexible toluene diisocyanate (TDI)-based polyurethane (PUR) foam were investigated. The foam was extracted using 0.1% (w/v) aqueous acetic acid (HAc). Extraction solutions were analysed and aromatic amines were determined as ethyl chloroformate (Et) and pentafluoropropionic acid anhydride (PFPA) derivatives. The determinations were performed using liquid chromatography (LC) and mass spectrometry (MS) detection with electrospray ionisation (ESI) or gas chromatography (GC)-MS with chemical ionisation monitoring negative ions (NCI). The Et derivatives were determined using LC-ESI+-MS with detection limit of 2 pg of toluenediamine (TDA). The PFPA derivatives were determined using LC-ESI--MS or GC-NCI-MS with detection limits of 0.1 and 0.02 pg of TDA, respectively. Using trideuterium labelled TDA as internal standard, linear calibration curves were obtained in the range of 0.01-0.50 mug ml(-1) (n = 7), with correlation coefficients >0.999. When plotting calibration curves for TDA-PFPA derivatives determined using LC-MS against TDA-PFPA using GC-MS and TDA-Et using LC-MS, linear curves were obtained. The relative standard deviation (R.S.D.) for determination of TDA in foam extraction solutions were 13%. LC-MS determination of PFPA derivatives was more selective, as compared to LC-MS of Et derivatives.

    In foam extraction solutions, 2,4- and 2,6-TDA, several isomers of methylenedianiline (MDA) and dimers of TDA/TDI were observed. 2,4-TDA and 4,4'-MDA are possible human carcinogens. Hydrolysis of the extraction solution revealed a large pool of TDA/TDI compounds and oligomers. The concentration of TDA in foam was affected by the extraction media, temperature and duration. The choice of derivatisation procedure also affected the determination of TDA. In extraction solutions from six different commercially available flexible foam qualities 2,4- and 2,6-TDA were found in the range of 0-7 and 0-6 mug g(-1) foam, respectively. When flexible foam was heated, considerable higher concentrations of TDA were observed.

  • 204.
    Marand, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Dalene, Marianne
    Skarping, Gunnar
    Solvent-free sampling with di-n-butylamine for monitoring of isocyanates in airManuscript (Other academic)
  • 205.
    Masala, Silvia
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of Polycyclic Aromatic Hydrocarbons in Various Environmental Matrices: Emphasis on extraction method development2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Very recently, air pollution was declared the world’s single largest environmental health risk by the World Health Organization. The goal of this thesis is to contribute to a better assessment of air pollution through the development of novel and exhaustive extraction methods for the analysis of polycyclic aromatic hydrocarbons (PAHs), which are mutagenic and carcinogenic air pollutants.

    The methods were developed and validated for the extraction of PAHs in both the semi-volatile fraction and particulate matter with application to samples derived from major sources of PAHs (diesel exhaust, coal fly ash and wood smoke samples). Pressurized liquid extraction was used because it allows a high sample throughput with reduced solvent requirements and analysis time compared to other traditionally used techniques, such as Soxhlet extraction.

    The results presented herein show that the extraction conditions used when analyzing PAHs need to be evaluated to avoid underestimating their concentrations. This is especially true for the human carcinogen benzo[a]pyrene, which is often used as an indicator in the cancer risk assessments of PAHs, and the dibenzopyrene isomers due to their potentially high carcinogenicities.

  • 206.
    Masala, Silvia
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Extraction of Polycyclic Aromatic Hydrocarbons (PAHs) in diesel and coal fly ash particulate matter: Emphasis on the carcinogenic benzo[a]pyrene and dibenzopyrene isomers2012Licentiate thesis, comprehensive summary (Other academic)
  • 207.
    Masala, Silvia
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ahmed, Trifa
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Improved efficiency of extraction of polycyclic aromatic hydrocarbons (PAHs) from the National Institute of Standards and Technology (NIST) Standard Reference Material Diesel Particulate Matter (SRM 2975) using accelerated solvent extraction2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 401, no 10, p. 3305-3315Article in journal (Refereed)
    Abstract [en]

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

  • 208.
    Masala, Silvia
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of benzo(a)pyrene and dibenzopyrenes in a Chinese coal fly ash Certified Reference Material2012In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 432, p. 97-102Article in journal (Other academic)
    Abstract [en]

    Air pollution from coal combustion is of great concern in China because coal is the country's principal source of energy and it has been estimated that coal combustion is one of the main sources of polycyclic aromatic hydrocarbon (PAH) emissions in the nation. This study reports the concentrations of 15 PAHs including benzo[a]pyrene, dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene in a coal fly ash certified reference material (CRM) from China. To the best of our knowledge, dibenzo[a,l]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene concentrations in coal fly ash particles have not previously been reported. Benzo[a]pyrene is the only one of the studied hydrocarbons whose concentration in the coal fly ash CRM had previously been certified. The concentration of this species measured in this present work was twice the certified value. This is probably because of the exhaustive accelerated solvent extraction method employed. Consecutive extractions indicated an extraction recovery in excess of 95% for benzo[a]pyrene. For the other determined PAHs, repeat extractions indicated recoveries above 90%.

  • 209.
    Masala, Silvia
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Rannug, Ulf
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Pressurized liquid extraction as an alternative to the Soxhlet extraction procedure stated in the US EPA method TO-13A for the recovery of polycyclic aromatic hydrocarbons adsorbed on polyurethane foam plugs2014In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 6, no 20, p. 8420-8425Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to develop a pressurized liquid extraction (PLE) method as an alternative to the relatively time consuming Soxhlet extraction procedure described in the United States Environmental Protection Agency (US EPA) method TO-13A for the extraction of PAHs adsorbed onto polyurethane foam plugs (PUFs). For this purpose PUF air samples were collected and split into two parts: one part extracted using PLE and the other one using Soxhlet extraction. Comparable PAH concentrations were obtained upon analysis of the extracts showing that the PLE method developed in this work is a more convenient choice than the commonly used Soxhlet extraction technique proposed by US EPA for the determination of PAHs in air samples. In fact, the developed PLE method required shorter assay times (minutes versus hours), less solvent consumption and simpler operational methods. The exhaustiveness of the developed PLE method was evaluated using repeat static extraction cycles, demonstrating an extraction efficiency for the PAHs of greater than 99%. The PLE method was then applied to diesel exhaust and wood smoke PUF samples showing an extraction efficiency for the PAHs of greater than 93% and 96%, respectively. Furthermore, a PLE method for PUF cleaning was developed as well and employed as an alternative to Soxhlet extraction. The PLE methods developed for cleaning and extracting PUFs presented in this work are suitable to be used in mutagenicity studies using the Ames Salmonella assay as no mutagenicity was found in the PLE generated blanks

  • 210.
    Melin, Jens
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sampling, characterisation and acute effects of isocyanates in aerosols: an occupational hygiene perspective2001Doctoral thesis, comprehensive summary (Other academic)
  • 211. Mie, Axel
    et al.
    Holst Laursen, Kristian
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Forshed, Jenny
    Lindahl, Anna
    Thorup-Kristensen, Kristian
    Olsson, Marie
    Knuthsen, Pia
    Huusfeldt Larsen, Erik
    Husted, Søren
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Discrimination of conventional and organic white cabbage from a long-term field trial study using untargeted LC-MS-based metabolomics2014In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 12, p. 2885-2897Article in journal (Refereed)
    Abstract [en]

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

  • 212.
    Moberg, Ludvig
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A multivariate approach to the analysis of phytoplankton pigments2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Photosynthetic pigments are routinely determined in investigations of marine and freshwater environments, chlorophyll is used as an estimator of phytoplankton biomass. Photosynthetic pigments are also widely used to characterise phytoplankton taxonomic composition. To estimate biomass from the chlorophyll a concentration, in vitro absorption and fluorimetric spectroscopic methods are used. However, these methods are known to be prone to interference from chlorophyll degradation products. If a taxonomical characterisation is required, i.e. identification of the phytoplankton classes present in a sample, these methods are inadequate.

    The objective of this thesis has been to develop qualitative and quantitative multivariate spectroscopic methods for the analysis of phytoplankton pigments. To evaluate the data in these studies, three chemometric methods have been used; principal component analysis (PCA), partial least squares regression (PLS) and parallel factor analysis (PARAFAC).

    A multivariate regression model, based on the absorption spectra of standards, was developed for the determination of the six key analytes (the chlorophylls and their degradation products), the chlorophylls were accurately determined in the presence of degradation products (Paper I). This method is validated, with real samples and samples harvested from laboratory cultures. The prediction results obtained with the proposed method were in good agreement with HPLC analysis, and for the cultures the results were consistent with prior knowledge about the pigment composition (Paper II). Absorption spectra and multivariate models were used for qualitative analysis of phytoplankton cultures and samples. Nine species representing six phytoplankton classes are analysed and the results demonstrated the possibility to assess the gross phytoplankton composition (Paper III). From samples collected in the Baltic Sea during one year, it was shown that a PCA model of the spectra yielded similar results as a PCA model of microscopy counts, which outlines the possibility to monitor and screen samples (Paper IV). Fluorescence excitation emission matrices were registered for a set of laboratory prepared standards, these were decomposed with a PARAFAC model and the obtained results were used for regression analysis. The second-order advantage was exploited which suspends the requirement of measuring all interfering constituents (Paper V). Excitation emission matrices are also measured in vivo for cultures and samples. From decomposition of the data it was found that four components attributed to the variation in the data. Two components were similar to chlorophyll and carotenoids and two components to phycobilines (manuscript). 

    In conclusion, the use of full spectrum techniques enhances the information acquired for phytoplankton samples, and chemometric methods have shown to be a valuable tool to extract this information.

  • 213.
    Moein, Mohammad Mahdi
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Towards more selective sorbents for extraction of drugs and biomarkers from biological fluids using molecularly imprinted polymers2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sample preparation has a critical role as a first step in analytical processes, especially in bioanalysis and environmental analysis. A good sample preparation technique should be robust and stable, regardless of the sample matrix.

    The aim of this thesis is to design and synthesize molecularly imprinted polymers that can be used in various sample preparation techniques, such as on-line MEPS, on-line SPE and on-line monolithic pre-columns used for the extraction of drugs, hormones, and cancer biomarkers from human plasma and urine samples. Additional aim was to provide full automation, on-line coupling, short sample preparation time and high-throughput.

    In this thesis MIP in MEPS was used on-line with liquid chromatography-tandem mass spectrometry (LC/MS/MS) for the determination of sarcosine in human urine and plasma samples. The method was fully automated and the packed sorbent could be used for about hundred extractions. In additional work a coated needle with MIP-Sol-Gel as thin layer was prepared and used for the microextraction of bilirubin from human plasma and urine. Small sample volumes could be handled and the validation of the method showed that the method was robust and selective.

    In a further work MIP-SPE on-line with HPLC was used for the extraction and determination of dextromethorphan in human plasma samples. MIP-SPE showed a good selectivity and high recovery (87% - 92%). On-line MIP monolithic pre-column was prepared and used in a coupled system for the extraction of tramadol in human plasma and urine samples. The MIP monolithic pre-column showed good selectivity and high extraction recovery was obtained (91-96%). The extraction and analysis of human insulin in plasma and pharmaceutical formulation solutions were carried out using MIP-SPE on-line with HPLC. The validation of the method showed that the method was accurate and robust.

  • 214.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Abbi
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of Sarcosine in Plasma and Urine Samples Utilizing Dummy Molecularly Imprinted Polymer and Microextraction by Packed Sorbent on-line with Liquid Chromatography Tandem Mass SpectrometryIn: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573Article in journal (Refereed)
  • 215.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Abbi
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Microextraction by packed sorbent (MEPS)2015In: TrAC. Trends in analytical chemistry, ISSN 0165-9936, E-ISSN 1879-3142, Vol. 67, p. 34-44Article in journal (Refereed)
    Abstract [en]

    Sample preparation is an important stage in separation and determination of components of interest from complex matrices. Sample preparation strongly influences the reliability and the accuracy of the analysis and the data quality. Recent trends in sample preparation include miniaturization, automation, high-throughput performance, on-line coupling with analytical instruments and low-cost operation using little or no solvent consumption. In the past decade, microextraction by packed sorbent (MEPS) was introduced as a simple, fast, on-line sample-preparation technique. Also, MEPS requires less sample and less solvent. This review gives an outline of the MEPS technique, including fields of application, common formats and sorbents, factors that affect performance, and the major advantages and limitations. Further, we offer and discuss our perspective on the future of MEPS.

  • 216.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Abbi
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    On-line determination of sarcosine in biological fluids utilizing dummy molecularly imprinted polymers in microextraction by packed sorbent2015In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 38, no 5, p. 788-795Article in journal (Refereed)
    Abstract [en]

    Several years ago, sarcosine received attention as a prostate-cancer marker. Prostate cancer is one of the most widespread types of tumor diseases in men. The prostate-specific antigen is normally used as a marker, and it can only be detected in blood with a sensitivity of approximately 80%. In the present study, dummy molecularly imprinted polymers in microextraction by packed sorbent with on-line liquid chromatography coupled to tandem mass spectrometry was used for the determination of sarcosine in human plasma and urine samples. The polymer network glycine was used for the dummy molecularly imprinted polymers. The selectivity of the method was evaluated using similar prostate-cancer biomarkers. In addition, various parameters affecting the extraction performance were investigated. The method limits of detection and quantification in the plasma and urine were 1.0 and 3.0 ng/mL, respectively. The values of the coefficient of determination were over 0.99 for all runs in the studied concentration range (3.0-10 000 ng/mL). The method recovery was 87 and 89% in plasma and urine, respectively. The intraday and interday precisions of sarcosine in the plasma and urine samples were in the ranges of 4.0-7.1, 3.0-6.3, 2.9-4.7, and 5.0-6.7, respectively.

  • 217.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    El-Beqqali, Aziza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Abbi
    Jeppsson-Dadoun, Amin
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Preparation of monolithic molecularly imprinted polymer sol-gel packed tips for high-throughput bioanalysis: Extraction and quantification of L-tyrosine in human plasma and urine samples utilizing liquid chromatography and tandem mass spectrometry2014In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 967, p. 168-173Article in journal (Refereed)
    Abstract [en]

    In situ monolithic molecularly imprinted polymer sol-gel packed tips (MMSTs) were prepared and evaluated for the extraction of lung cancer biomarker L-tyrosine (Tyr) from human plasma and urine samples. Several extraction parameters such as the conditioning, washing and elution solutions, pH and time were investigated. The enrichment factor (EF) and extraction recovery (ER) were studied. MMST showed good selectivity and a high extraction recovery, and MMST as a sorbent showed good stability and repeatability. The method validation showed good regression correlation coefficients for plasma and urine samples (R-2 >= 0.996) within the concentration range of 5-1000 and 1-1000 nmol L-1 in plasma and urine samples, respectively. The lower limits of quantification (LLOQ) in the plasma and urine samples were 5 and 1 nmol L-1, respectively. The between-batch precision for Tyr in plasma ranged from 1.0 to 6.0%, and in urine it was from 1.0 to 7.0%. The results show that the developed method has more facility, stability, durability and repeatability compared with previous similar methods. To the best of our knowledge, this is the first study aimed at the selective separation of Tyr as a lung cancer biomarker by MMSTs from biological matrixes and detection by LC/MS/MS.

  • 218. Moein, Mohammad Mahdi
    et al.
    El-Beqqali, Aziza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Javanbakht, Mehran
    Karimi, Mohammad
    Akbari-adergani, Behrouz
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    On-line detection of hippuric acid by microextraction with a molecularly-imprinted polysulfone membrane sorbent and liquid chromatography-tandem mass spectrometry2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1372, p. 55-62Article in journal (Refereed)
    Abstract [en]

    Destruction of sorbents during consecutive extractions using the microextraction by packed sorbent (MEPS) technique is a serious problem. In MEPS the complex matrix such as plasma and blood can affect the sorbent physical properties and the sorbent can be deteriorated after handling of few samples. To overcome this problem, the surface of a polysulfone membrane (PSM) was modified by a molecularly imprinted sol-gel and utilized for online extraction of a lung cancer biomarker, hippuric acid (HA), in biological matrices. The molecularly imprinted polymer membrane provided fast, sensitive, selective and robust sample preparation method for HA in biological fluids. In addition, MIP membrane could be used for up to 50 extractions without a significant change in extraction recovery. To achieve the best results, the parameters that influenced the extraction efficiency were thoroughly investigated. Moreover, for evaluating the performance of the molecularly imprinted sol-gel membrane (MISM), a non-molecularly imprinted sol-gel membrane (NISM) as a blank was prepared. The limits of detection CLOD) and quantification (LOQ) for HA in both plasma and urine samples were 0.30 nmol L-1 and 1.0 nmol L-1, respectively. Standard calibration curves were obtained over the range of 1-1000 nmol L-1 for HA in plasma and urine samples. The coefficients of determination (R2) were ≥ 0.997. The extraction recoveries of HA from human plasma and urine samples were higher than 91%. The precision values for HA in plasma and urine samples were 2.2-4.8% and 1.1-6.7%, respectively.

  • 219.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jabbar, Dunia
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A needle extraction utilizing a molecularly imprinted-sol-gel xerogel for on-line microextraction of the lung cancer biomarker bilirubin from plasma and urine samples2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1366, p. 15-23Article in journal (Refereed)
    Abstract [en]

    In the present work, a needle trap utilizing a molecularly imprinted sal-gel xerogel was prepared for the on-line microextraction of bilirubin from plasma and urine samples. Each prepared needle could be used for approximately one hundred extractions before it was discarded. Imprinted and non-imprinted sol-gel xerogel were applied for the extraction of bilirubin from plasma and urine samples. The produced molecularly imprinted sol-gel xerogel polymer showed high binding capacity and fast adsorption/desorption kinetics for bilirubin in plasma and urine samples. The adsorption capacity of molecularly imprinted sal-gel xerogel polymer was approximately 60% higher than that of non-imprinted polymer. The effect of the conditioning, washing and elution solvents, pH, extraction time, adsorption capacity and imprinting factor were investigated. The limit of detection and the lower limit of quantification were set to 1.6 and 5 nmol L-1, respectively using plasma or urine samples. The standard calibration curves were obtained within the concentration range of 5-1000 nmol L-1 in both plasma and urine samples. The coefficients of determination values (R-2) were >= 0.998 for all runs. The extraction recovery was approximately 80% for BR in the human plasma and urine samples.

  • 220.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jabbar, Dunia
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A novel needle trap utilizing molecularly imprinted-sol-gel xerogel for on-line microextraction of lung cancer biomarker bilirubin from plasma and urine samplesIn: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778Article in journal (Refereed)
  • 221. Moein, Mohammad Mahdi
    et al.
    Javanbakht, Mehran
    Karimi, Mohammad
    Akbari-Adergani, Behrouz
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A new strategy for surface modification of polysulfone membrane by in situ imprinted sol-gel method for the selective separation and screening of L-Tyrosine as a lung cancer biomarker2015In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 140, no 6, p. 1939-1946Article in journal (Refereed)
    Abstract [en]

    In this work, a novel method based on in situ molecularly imprinted sol-gel for the surface modification of a polysulfone membrane (PSM) was developed. A modified molecularly imprinted sol-gel polysulfone membrane (MSM) was placed in a homemade plastic tube and coupled on-line with LC/MS/MS for the selective extraction and screening of L-Tyrosine (Tyr) as a tentative lung cancer biomarker in human plasma samples. The existence of molecularly imprinted sol-gel layers on both sides of a PSM was examined using scanning electron microscopy (SEM). To evaluate the role of precursor in the extraction performance, repeatability, and selectivity of developed method, three precursors, 3-(propylmethacrylate) trimethoxysilane (P1), 3-(triethoxysilyl)-propylamine (P2), tetraethyl orthosilicate (P3), individually and together were used for treatment of PSM. Our investigation showed that a single precursor's route is more repeatable, straightforward, precise, accurate, and selective for the extraction of Tyr in plasma samples. Moreover, to achieve the best conditions and extraction efficiency, the effect of influential parameters, including the conditioning, washing, and elution of solvents, sample flow rate, loading time, desorption time, loading sample volume, salt effect, pH, and adsorption capacity for the most efficiently prepared membranes were truly investigated. The non-molecularly imprinted sol-gel polysulfone membrane (NSM) was prepared as a blank via the same process but in the absence of the Tyr. The LOD (S/N = 3/1) was 0.1 nmol L-1 and the LOQ (S/N = 10/1) was 0.34 nmol L-1 for Tyr in the plasma samples. The linearity for the Tyr was in the range of 0.34-2000 nmol L-1 in the plasma samples. The coefficients of determination values were >= 0.998 for all runs. The extraction recovery was between 80%-85% for Tyr in the plasma samples. In addition, MSM could be used for up to 50 extractions without a significant change in recovery percentage.

  • 222.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. Amirkabir University of Technology, Iran.
    Said, Rana
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bassyouni, Fatma
    Abdel-Rehim, Andmohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. National Research Centre, Egypt.
    Solid Phase Microextraction and Related Techniques for Drugs in Biological Samples2014In: Journal of Analytical Methods in Chemistry, ISSN 2090-8865, E-ISSN 2090-8873, p. 921350-Article, review/survey (Refereed)
    Abstract [en]

    In drug discovery and development, the quantification of drugs in biological samples is an important task for the determination of the physiological performance of the investigated drugs. After sampling, the next step in the analytical process is sample preparation. Because of the low concentration levels of drug in plasma and the variety of the metabolites, the selected extraction technique should be virtually exhaustive. Recent developments of sample handling techniques are directed, from one side, toward automatization and online coupling of sample preparation units. The primary objective of this review is to present the recent developments in microextraction sample preparation methods for analysis of drugs in biological fluids. Microextraction techniques allow for less consumption of solvent, reagents, and packing materials, and small sample volumes can be used. In this review the use of solid phase microextraction (SPME), microextraction in packed sorbent (MEPS), and stir-bar sorbtive extraction (SBSE) in drug analysis will be discussed. In addition, the use of new sorbents such as monoliths and molecularly imprinted polymers will be presented.

  • 223.
    Möller, Kristina
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Molecularly Imprinted Solid-Phase Extraction and Liquid Chromatography for Biological Samples2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on the use of molecularly imprinted polymers as selective sorbents for solid-phase extraction (MISPE). The MISPE methods developed were mainly intended for use with biological samples, such as human urine and blood plasma. These body fluids are complex samples, which often need an effective clean-up step before analysis to reduce the levels of possible interfering substances from the matrix, especially if the analytes are present in trace amounts. Solid-phase extraction (SPE) is a well-established and routinely used method for clean-up and preconcentration of samples from diverse matrices. However, conventional SPE sorbents often lack selectivity, leading to co-extraction of interferences, which negatively affects the following detection method. One of the advantages of MISPE is the built-in selectivity for a target analyte, or class of structurally related analytes, enabling the efficient clean-up that is often required for biological samples. The built-in selectivity of MISPE originates from the preparation of a highly crosslinked copolymer network in the presence of an imprint molecule, i.e. the template. Subsequent removal of this template molecule leads to the creation of defined recognition sites, complementary to the shape and functionality of the template.

    In this work, molecularly imprinted polymers were synthesized for the first time for several types of target analytes, including diphosphate esters (Papers I-III) and a protein adduct (Paper IV) and evaluated as sorbents for solid-phase extraction. A MISPE method for extracting local anaesthetic drugs from human plasma was also evaluated (Paper V). The development of appropriate methods for using the prepared polymers to extract target analytes directly from body fluids, and the elucidation of factors that influence their performance, were major foci of all the work underlying this thesis. These are not straightforward tasks, since the recognition mechanism of the material is often based on polar interactions, which are not favoured in aqueous environments. In such cases, non-selective adsorption of the analyte(s) to the polymer surface often occurs. In order to use the MIP sorbent most effectively it is important to suppress this non-selective adsorption, without disrupting the selective adsorption of the target analyte(s) to the imprints. Generally in these studies, this strong analyte-polymer surface interaction could be repressed, and selective adsorption enhanced, by carefully optimising the conditions for washing the sorbent, in terms of organic solvent volumes, solvent polarity and the addition of an ionic modifier. The sample matrix, mainly urine, was found to strongly decrease the capacity of the MIP. Hence, this effect was further investigated. It was found that the presence of NaCl in the sample negatively affected the recovery and repeatability of the method. Furthermore, these parameters could be improved by adjusting the sample pH. It was important to control the pH of the sample, in order both to achieve selective extraction and to increase the extraction recoveries. The selectivity of MISPE for the extraction of diphosphate esters from human urine was demonstrated by comparing its performance with that of a conventional SPE sorbent, a mixed-mode-anion exchanger (MAX). Due to its efficient clean-up, MISPE generated extracts that yielded less complex ion chromatograms in subsequent LC/ESI-MS analysis than extracts from the MAX cartridge. Due to its efficient clean-up, MISPE generated extracts that yielded less complex ion chromatograms in subsequent LC/ESI-MS analysis than extracts from the MAX cartridge. Signal suppression from the interfering co-eluting compounds was detected when the MAX extracts were analysed, which was not the case for the MISPE extracts. These findings show the importance of efficient and selective sample preparation, even if a selective detector is used.

    Development of LC/ESI-MS methods was also an extensive component of this work (Papers I-IV). Different chromatographic conditions have been evaluated for the optimal separation and detection of the investigated compounds. Use of ion-pairing agents and suitable HPLC columns (Hypercarb and C18 Aquasil) for the acidic, polar analytes, was found to give better retention and separation than use of conventional reversed-phase columns. To improve the selectivity and detectability further, selected ion monitoring (SIM) and selected reaction monitoring (SRM) acquisition modes were used for quantification of the investigated compounds.

    In summary, the aim of this work was to contribute to the knowledge of the recognition mechanisms of molecularly imprinted polymers in aqueous matrices, which is important for extending the use of MISPE for several types of bioanalytical applications.

  • 224.
    Möller, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Nilsson, Ulrika
    Determination of a flame retardant hydrolysis product in human urine by SPE and LC-MS. Comparison of molecularly imprinted solid-phase extraction with a mixed-mode anion exchanger2004In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, Vol. 378, no 1, p. 197-204Article in journal (Refereed)
  • 225. 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, p. 2497-2501Article 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.

  • 226.
    Möller, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Crescenzi, Carlo
    Investigation of matrix effects on a molecularly imprinted solid-phase extraction2004In: Journal of Chromatography B, ISSN 1570-0232, Vol. 811, no 2, p. 171-176Article in journal (Refereed)
  • 227.
    Möller, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Crescenzi, Carlo
    Synthesis and evaluation of molecularly imprinted polymers for extracting hydrolysis products of organophosphate flame retardants2001In: Journal of Chromatography A, ISSN 0021-9673, Vol. 938, no 1-2, p. 121-130Article in journal (Refereed)
  • 228.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Properties of some chlorinated polycyclic aromatic hydrocarbons with respect to chemical analysis1992Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes chemical and biological properties of chloro-added and chloro-substituted PAHs with respect to chemical analysis. The work includes biological testing with Ames assay, study of chemical reactivities in chlorination reactions and retention characteristics on normal phase stationary phases for HPLC, as well as analysis of urban air samples with respect to chlorinated PAHs (Cl-PAHs).

    A clean-up method for Cl-PAHs in ambient air samples was developed. This involves back-flush HPLC with a cyanopropyl-bonded stationary phase for isolation of chloro-added PAHs and a two-dimensional HPLC back-flush method, utilizing coupled nitrophenylpropylsilyl and 2-(l-pyrenyl)ethylsilyl columns, for isolation of chloro-substituted PAHs.

    Several chloro-substituted PAHs, of which some have shown significant mutagenic effects on Salmonella typhimurium bacterial strains in the Ames assay, were identified and quantified in urban air. Further, chloro-substituted PAHs which may derive from biologically active and highly unstable chloroadded derivatives were detected. The postulation that automobile traffic is a major source of chlorinated PAHs in urban air, was supported by the higher levels detected of these in samples from an intensively trafficked road tunnel. Furthermore, the concentration profiles of the Cl-PAHs detected in the road tunnel and in the urban air showed large similarities.

    An LC-GC-MS method was developed for on-line clean-up and analysis of Cl-PAHs in order to facilitate analysis of small air volumes. The method showed high reproducibility and precision and could be applied to personal exposure measurements in work environment. Determinations were made on exposure of bus drivers, with driving routes located in the inner part of Stockholm. Four chlorosubstituted PAHs, of which two monochloropyrenes were quantified, were detected in the samples.

  • 229.
    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)
  • 230.
    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, p. 2784-2790Article 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

  • 231. Nordin, Erik Z.
    et al.
    Uski, Oskari
    Nyström, Robin
    Jalava, Pasi
    Eriksson, Axel C.
    Genberg, Johan
    Roldin, Pontus
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jokiniemi, Jorma
    Pagels, Joakim H.
    Boman, Christoffer
    Hirvonen, Maija-Riitta
    Influence of ozone initiated processing on the toxicity of aerosol particles from small scale wood combustion2015In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 102, p. 282-289Article in journal (Refereed)
    Abstract [en]

    Black carbon containing emissions from biomass combustion are being transformed in the atmosphere upon processing induced by tropospheric ozone and UV. The knowledge today is very limited on how atmospheric processing affects the toxicological properties of the emissions. The aim of this study was to investigate the influence of ozone initiated (dark) atmospheric processing on the physicochemical and toxicological properties of particulate emissions from wood combustion. Emissions from a conventional wood stove operated at two combustion conditions (nominal and hot air starved) were diluted and transferred to a chamber. Particulate matter (PM) was collected before and after ozone addition to the chamber using an impactor. Detailed chemical and physical characterization was performed on chamber air and collected PM. The collected PM was investigated toxicologically in vitro with a mouse macrophage model, endpoints included: cell cycle analysis, viability, inflammation and genotoxicity. The results suggest that changes in the organic fraction, including polycyclic aromatic hydrocarbons (PAHs) are the main driver for differences in obtained toxicological effects. Fresh hot air starved emissions containing a higher organic and PAH mass-fraction affected cell viability stronger than fresh emissions from nominal combustion. The PAH mass fractions decreased upon aging due to chemical degradation. Dark aging increased genotoxicity, reduced viability and reduced release of inflammatory markers. These differences were statistically significant for single doses and typically less pronounced. We hypothesize that the alterations in toxicity upon simulated dark aging in the atmosphere may be caused by reaction products that form when PAHs and other organic compounds react with ozone and nitrate radicals. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).

  • 232.
    Nordqvist, Yvonne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Development and Evaluation of a Denuder-Filter System Designed for Sampling Diisocyanate Aerosols2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There are many occupational environments in which isocyanates or PUR-products are used, produced or processed. During these operations there is always a risk of isocyanate exposure, which may lead to severe health problems. Isocyanates principally affect the respiratory system and they are the main cause of occupational asthma. The prevalence of asthma among exposed workers is generally 5-10%, according to most studies, but figures as high as 30% have been reported.

    The most commonly used isocyanates may occur in both vapour and particulate forms. Their physical state may affect both their deposition in the airways and their impact on health. Nevertheless, the occupational exposure limit for isocyanates applies to the total amount of isocyanates present, regardless of their physical state. Setting different exposure limits for vapour and particles would require the air sampling step to be capable of separating and independently measuring the phases. This is not straightforward, since every sampling method may be affected by a number of possible sampling artefacts. To minimize such biases, a profound knowledge of the sampling system and its behaviour is required.

    In this thesis a chemosorptive cylindrical denuder and filter, connected to a sampling pump, has been developed for personal exposure measurements of isocyanates. The model compounds for the investigation and evaluation were some of the most commonly used diisocyanates in industry: toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and methylene diphenyl diisocyanate (MDI).

    Using a combination of dimethylpolysiloxane (SE-30) and dibutylamine (DBA) as a chemosorptive coating on both the inner wall of the denuder tube and the filter, the derivatisation was shown to be fast enough for efficient collection of the isocyanates. The repeatability of the air measurements was high, with variabilities generally between 5-10% in the measured concentration range. 15-min samplings were performed of both vapour and aerosols of nm-size, from below the OEL (5ppbv) up to 235 ppbv, without exceeding the coating capacity or causing breakthrough due to chromatographic movement. At the applied airflow rates, between 50 and 500 ml/min, the breakthrough, i.e. the percentage of the TDI vapour that passes through the denuder tube ending up on the filter, was shown to be consistent with amounts predicted by the Gormley-Kennedy equation. For isocyanate aerosols, extensive gas-stripping was shown to occur inside the denuder tube at the lower end of the investigated flow range. This phenomenon was minimized when a flow rate between 300 and 500 ml/min was applied (Papers III-IV).

    The great advantage of a denuder sampler compared to wet methods, such as the commonly used impinger method, is its suitability for personal exposure measurements. Due to its small size and absence of solvent it is more convenient to carry during a work shift. Furthermore, the results in Paper II indicate that 8-hour denuder measurements can be performed without detectable breakthrough of the vapour phase. The derivatives formed during the sampling of isocyanates were shown to be stable in the samplers for several days after the measurements were finished, provided both the denuder tubes and filters were stored in the freezer and in solvent containing excess reagent. Furthermore, filters and tubes could be prepared at least 4 d prior to sampling, without loss of performance. This is highly relevant to the applicability of the method for field measurements.

    Both LC-ESI-MS (Paper II-IV) and LC-APCI-MS (Paper I) were used to determine the analytes in the air samples. The former method exhibited the lowest detection limit for the isocyanate-DBA derivatives. Using selected reaction monitoring (SRM) the obtained method detection limit for the investigated compounds was below 10 ng/m3.

  • 233.
    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, p. 39-43Article 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.

     

  • 234.
    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, p. 786-791Article 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.

  • 235.
    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, p. 1294-9Article in journal (Other academic)
  • 236.
    Nordqvist, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Colmsjö, Anders
    Investigation of a cylindrical chemosorptive denuder for sampling and phase separation of toluene diisocyanate aerosols2005In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 382, no 5, p. 1294-1299Article in journal (Refereed)
    Abstract [en]

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

  • 237.
    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.))
  • 238.
    Olsson, Petter
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Holmbäck, Jan
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Herslöf, Bengt
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A single step reversed-phase high performance liquid chromatography separation of polar and non-polar lipids2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1369, p. 105-115Article in journal (Refereed)
    Abstract [en]

    This paper reports a simple chromatographic system to separate lipids classes as well as their molecular species. By the use of phenyl coated silica as stationary phase in combination with a simple mobile phase consisting of methanol and water, all tested lipid classes elute within 30min. Furthermore, a method to accurately predict retention times of specific lipid components for this type of chromatography is presented. Common detection systems were used, namely evaporative light scattering detection (ELSD), charged aerosol detection (CAD), electrospray mass spectrometry (ESI-MS), and UV detection.

  • 239.
    Olsson, Petter
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Holmbäck, Jan
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Herslöf, Bengt
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Separation of Lipid Classes by HPLC on a Cyanopropyl Column2012In: Lipids, ISSN 0024-4201, E-ISSN 1558-9307, Vol. 47, no 1, p. 93-99Article in journal (Refereed)
    Abstract [en]

    A new method for the separation and identification of lipid classes by normal-phase HPLC on a cyanopropyl column is described. The use of a simple binary gradient, with toluene as a component, provided a rapid separation of non-polar as well as phospholipid classes. The inherent small differences in performances between possible non-polar eluent components of the gradient, such as hexane, heptane, and iso-octane, had a pronounced impact on retention times for individual phospholipid classes. Separation of molecular species within a lipid class could also be observed.

  • 240.
    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, p. 653-658Article 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.

  • 241.
    Olsson, Petter
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Holmbäck, Jan
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Class separation of lipids and polycyclic aromatic hydrocarbons in normal phase high performance liquid chromatography - A prospect for analysis of aromatics in edible vegetable oils and biodiesel exhaust particulates2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1360, p. 39-46Article in journal (Refereed)
    Abstract [en]

    The retention characteristics of the major lipid components in biodiesels and edible oils as well as representative polycyclic aromatic compounds (PAHs) have been investigated on five different normal phase HPLC stationary phases, in order to optimize class separation for an automatized online HPLC cleanup of PAHs prior GC-MS analysis. By stepwise comparison of different hexane/MTBE compositions as mobile phases on cyano-, phenyl-, pentabromobenzyl-, nitrophenyl- and amino- modified silica columns, the capacity and selectivity factors for each analyte and column could be calculated. It was concluded that the most suitable column for backflush isolation of PAHs in biodiesel and edible oil matrices was the pentabromobenzyl-modified silica (PBB). A previously described online HPLC-GC-MS system using the PBB column was then evaluated by qualitative and quantitative analysis of a biodiesel exhaust particulate extract and a vegetable oil reference material. The GC-MS full scan analysis of the biodiesel particulate extract showed that the lipids had been removed from the sample and a fraction containing PAHs and oxygenated derivatives thereof had been isolated. Quantified mass fractions of PAHs of the reference material BCR-458 agreed well for most of the certified PAH mass fractions in the spiked coconut oil reference material.

  • 242.
    Oskarsson, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wiklund, Ann-Kristin Eriksson
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Thorsén, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Danielsson, Gabriela
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Kumblad, Linda
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Community Interactions Modify the Effects of Pharmaceutical Exposure: A Microcosm Study on Responses to Propranolol in Baltic Sea Coastal Organisms2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 4, article id e93774Article in journal (Refereed)
    Abstract [en]

    This study investigated the uptake and effects of a common human pharmaceutical, propranolol, on the structure and function of a coastal Baltic Sea model community consisting of macroalga (Ceramium tenuicorne), mussels (Mytilus edulis trossulus), amphipods (Gammarus spp.), water and sediment. The most sensitive species, the mussel, was affected to the same extent as in previous single species studies, while the effects on the amphipod and alga were smaller or even positive compared to experiments performed in less complex test systems. The observed cascade of beneficial effects was a result of inter-specific species interactions that buffered for more severe effects. The poor condition of the mussel led to a feeding shift from alga to mussel by the amphipods. The better food quality, due to the dietary shift, counteracted the effects of the exposure. Less amphipod grazing, together with increased levels of nutrients in the water was favourable for the alga, despite the negative effects of propranolol. This microcosm study showed effects on organisms on different organizational levels as well as interactions among the different components resulting in indirect exposure effects of both functional and structural nature. The combination of both direct and indirect effects would not have been detected using simpler single- or even two-species study designs. The observed structural changes would in the natural environment have a long-term influence on ecosystem function, especially in a low-biodiversity ecosystem like the Baltic Sea.

  • 243.
    Pauter, Anna M.
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Olsson, Petter
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Asadi, Abolfazl
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Herslöf, Bengt
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Csikasz, Robert I.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Zadravec, Damir
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Jacobsson, Anders
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Elovl2 ablation demonstrates that systemic DHA is endogenously produced and is essential for lipid homeostasis in mice2014In: Journal of Lipid Research, ISSN 0022-2275, E-ISSN 1539-7262, Vol. 55, no 4, p. 718-728Article in journal (Refereed)
    Abstract [en]

    The potential role of endogenously synthesized polyunsaturated fatty acids (PUFAs) is a highly overlooked area. Elongation of very long chain (ELOVL) fatty acids in mammals is catalyzed by the ELOVL enzymes to which the PUFA elongase ELOVL2 belongs. To determine its in vivo function, we have investigated how ablation of ELOVL2, which is highly expressed in liver, affects hepatic lipid composition and function in mice. The Elovl2 ablated mice displayed substantial decreased levels of 22:6(n3), docosahexaenoic acid (DHA), and 22:5(n6), docosapentaenoic acid (DPAn6), followed by an accumulation of 22:5(n3) and 22:4(n6) in both liver and serum showing that ELOVL2 primarily controls the elongation process of PUFAs with 22 carbons to produce 24 carbon precursors for DHA and DPA(n6) formation in vivo. The impaired PUFA levels positively influenced hepatic levels of the key lipogenic transcriptional regulator sterol regulatory element binding protein 1c (SREBP1c) as well as its downstream target genes. Surprisingly, the Elovl2 ablated mice were resistant against hepatic steatosis and diet induced weight gain implying that hepatic DHA synthesis via ELOVL2, except controlling de novo lipogenesis, also regulates lipid storage and fat mass expansion in an SREBP1c independent fashion. The changes in fatty acid metabolism were reversed by dietary supplementation with DHA.

  • 244. Pereira, Jorge
    et al.
    Camara, Jose S.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. National Research Center, Egypt.
    Microextraction by packed sorbent: an emerging, selective and high-throughput extraction technique in bioanalysis2014In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 28, no 6, p. 839-847Article in journal (Refereed)
    Abstract [en]

    Sample preparation is an important analytical step regarding the isolation and concentration of desired components from complex matrices and greatly influences their reliable and accurate analysis and data quality. It is the most labor-intensive and error-prone process in analytical methodology and, therefore, may influence the analytical performance of the target analytes quantification. Many conventional sample preparation methods are relatively complicated, involving time-consuming procedures and requiring large volumes of organic solvents. Recent trends in sample preparation include miniaturization, automation, high-throughput performance, on-line coupling with analytical instruments and low-cost operation through extremely low volume or no solvent consumption. Micro-extraction techniques, such as micro-extraction by packed sorbent (MEPS), have these advantages over the traditional techniques. This paper gives an overview of MEPS technique, including the role of sample preparation in bioanalysis, the MEPS description namely MEPS formats (on- and off-line), sorbents, experimental and protocols, factors that affect the MEPS performance, and the major advantages and limitations of MEPS compared with other sample preparation techniques. We also summarize MEPS recent applications in bioanalysis.

  • 245.
    Pettersen, Harald
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Aspects of aquatic sampling and exploratory data analysis of hydrophobic organic compounds1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on seven papers describing studies conducted with samples from the Baltic Sea. It discusses some aspects on the use of multivariate methods for evaluation of data on hydrophobic organic compounds (HOCs) found in the aquatic environment. The HOCs studied are primarily polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), and the matrices mainly samples of recent soft bottom sediments and settling particles.

    The multivariate studies, performed in six of the seven papers, were all conducted using the pattern recognition (PARC) methods principal component analysis (PCA) and the classification method SIMCA. The PARC methods are applied on chemical profiles, i.e. the relative levels of compounds in a sample. Methods for pre-processing of data prior to PARC are also discussed.

    The results are discussed from a chemical point of view concerning the chemistry of HOCs in terms of environmental behaviour, and also from an ecological perspective concerning their sources, transport and distribution. Most of the multivariate studies concern the spatial distribution of compounds of the same type. These studies can be divided into attempts to differentiate samples taken at or near sources of HOCs from background samples, and to study the distribution of HOCs in remote areas.

    PARC was also used to differentiate between the distribution of different groups of HOCs (i.e. pesticides), and to show that the PAH profile changes with depth in a sediment, whereas the PCB profile does not.

    Conclusively, the thesis shows that a combination of PARC methods is a versatile tool for different types of studies concerning HOCs in the aquatic environment.

    A novel method for estimating the degree of resuspended sedimentary material found in sediment traps is also presented. The method uses stable carbon isotope values of individual PAHs as labels of sedimentary input to the traps.

    Some aspects on the variations associated with sampling of sediments for HOC analysis are also discussed. This study clearly shows that the sampling procedure itself introduces most of the variation, followed by spatial variations in the sediments. The analytical procedure has the smallest effect on the variation.

  • 246. Pettersson, Esbjoern
    et al.
    Boman, Christoffer
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bostroem, Dan
    Nordin, Anders
    Stove Performance and Emission Characteristics in Residential Wood Log and Pellet Combustion, Part 1: Pellet Stoves2011In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, no 1, p. 307-314Article in journal (Refereed)
  • 247. Pettersson, Esbjorn
    et al.
    Boman, Christoffer
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bostrom, Dan
    Nordin, Anders
    Stove Performance and Emission Characteristics in Residential Wood Log and Pellet Combustion, Part 2: Wood Stove2011In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, p. 315-323Article in journal (Refereed)
    Abstract [en]

    The characteristics and quantities of a large number of gaseous and particulate emission components during combustion in a residential wood log stove with variations in fuel, appliance and operational conditions were determined experimentally. The measurement campaign included CO, NO(x), organic gaseous carbon (OGC), volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), total particulate matter (PM(tot)) as well as particle mass and number concentrations, size distributions, and inorganic composition. CO varied in the range of 1100 to 7200 mg/MJ(fuel), while OGC varied from 210 to 3300 mg/MJ(fuel). Dominating VOCs were methane, followed by ethene, acetylene, and benzene. Methane varied from 9 to 1600 mg/MJ(fuel). The nonmethane volatile organic compound (NMVOC) emissions were in the range of 20-2300 mg/MJ(fuel). The PAH(tot) emissions varied from 1.3 to 220 mg/MJ(fuel), in most cases dominated by phenantrene, fluoranthene, and pyrene. PM(tot) were in all cases dominated by fine particles and varied in the range 38-350 mg/MJ(fuel). The mass median particle diameters and the peak mobility diameters of the fine particles varied in the range 200-320 and 220-330 nm, respectively, and number concentrations in the range of 1-4 x 10(13) particles/MJ(fuel). Air starved conditions, at high firing intensity, gave the highest emissions, especially for hydrocarbons. This type of condition is seldom considered, though it may occur occasionally. The emissions from Swedish wood stoves, comparing a Swedish field study, are covered fairly well with the applied methodology, but other field studies report considerably higher emissions especially for diluted particle sampling.

  • 248. Pettersson, Esbjörn
    et al.
    Lindmark, Fredrik
    Öhman, Marcus
    Nordin, Anders
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Boman, Christoffer
    Design Changes in a Fixed-Bed Pellet Combustion Device: Effects of Temperature and Residence Time on Emission Performance2010In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 24, no 2, p. 1333-1340Article in journal (Refereed)
    Abstract [en]

    The use of wood fuel pellets has proven to be well-suited for the small-scale market, enabling controlled and efficient combustion with low emission of products of incomplete combustion (PIC). Still! a potential for further emission reduction exists, and it thorough understanding of the influence of combustion Conditions oil the emission characteristics of air pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and particulate matter (PM), is important. The Objective of the present work was to determine the effect of design changes, i.e., increasing the temperature and/or residence time, on the emission performance and characteristics for a pellet combustion device using a laboratory fixed-bed reactor (< 5 kW) The temperature and residence time after the bed Section were varied according to statistical experimental designs (650-950 degrees C and 0.5-3.0 s) with file emission responses: CO, organic gaseous carbon (OGC), NO, volatile organic compounds (VOCs, 20 compounds), PAHs (43 compounds), PMtot mass concentration, fine particle mass/count median diameter (MMD and CMD), and number concentration. The temperature was negatively correlated with the emissions of all studied PIC, with limited effects of the residence time. The PMtot emissions of 15-20 mg/MJ were in all cases dominated by fine (< 1 mu m) particles of K, Na, S, Cl, C, O, and Zn. An increased residence time resulted in increased fine particle sizes (i.e., MMD and CMD) and decreased number concentrations. The Importance of a high temperature (> 850 degrees C in the bed zone with intensive, air-rich, and well-mixed Conditions was illustrated for wood pellets combustion with almost a total depletion Of all Studied PIC. The importance of the residence time was shown to be limited, and file results emphasize the need for further verification studies and technology development work.

  • 249. Pettersson, Johan
    et al.
    Aldaeus, Fredrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Kloskowski, Adam
    Roeraade, Johan
    Ultra thick film open tubular traps with an increased inner diameter2004In: Journal of Chromatography A, Vol. 1047, p. 93–99-Article in journal (Refereed)
  • 250.
    Pisareva, Tatiana
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Shumskaya, Maria
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Maddalo, Gianluca
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Norling, Birgitta
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Proteomics of Synechocystis sp. PCC 6803 Identification of novel integral plasma membrane proteins: Identification of novel integral plasma membrane proteins2007In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 274, no 3, p. 791-804Article in journal (Refereed)
    Abstract [en]

    The cyanobacterial plasma membrane is an essential cell barrier with functions such as the control of taxis, nutrient uptake and secretion. These functions are carried out by integral membrane proteins, which are difficult to identify using standard proteomic methods. In this study, integral proteins were enriched from purified plasma membranes of Synechocystis sp. PCC 6803 using urea wash followed by protein resolution in 1D SDS/PAGE. In total, 51 proteins were identified by peptide mass fingerprinting using MALDI-TOF MS. More than half of the proteins were predicted to be integral with 1–12 transmembrane helices. The majority of the proteins had not been identified previously, and include members of metalloproteases, chemotaxis proteins, secretion proteins, as well as type 2 NAD(P)H dehydrogenase and glycosyltransferase. The obtained results serve as a useful reference for further investigations of the address codes for targeting of integral membrane proteins in cyanobacteria.

2345678 201 - 250 of 370
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf