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  • 1.
    Aldaeus, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thewalim, Yasar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Prediction of retention times and peak widths in temperature-programmed gas chromatography using the finite element method2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 1, p. 134-139Article in journal (Refereed)
    Abstract [en]

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

  • 2.
    Aldaeus, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thewalim, Yasar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Prediction of retention times of polycyclic aromatic hydrocarbons and n -alkanes in temperature-programmed gas chromatography2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 389, no 3, p. 941-950Article in journal (Refereed)
    Abstract [en]

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

  • 3.
    Colmsjö, Anders
    Stockholm University.
    The practice and utility of the Shpol'skii effect in chemical analysis1981Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is an attempt to establish the Shpol' skii fluorescence as a valuable tool for analytical chemists. The basic principles of the Shpol'- skii fluorescence is comprehensively explained and the most important parameters that influence the registering of quasilinear spectra are discussed.

    The sample compartment that is needed for proper registration of Shpol' skii spectra is optimized with respect to inner filter effects and adapted for low temperature use. The temperature used in these investigations was mostly 63 K (-210°C).

    The identifying of chemical compounds by aid of their Shpol' skii spectra is primarily made by utilizing the fingerprint identification technique, i.e. to utilize the, for each Shpol' skii emitting compound characteristic, narrow-banded fluorescence spectrum.

    The analysis of samples from ambient air, soil, automobile exhaust, petroleum products, etc. by aid of cleaning up steps, HPLC and quasilinear fluorescence are demonstrated and evaluated and the selectivity of the method is discussed. The appearance of unidentified spectra in real sample analysis is briefly discussed and the establishing of a large reference library is emphasized.

  • 4.
    Daryanavard, Seyed
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jeppsson-Dadoun, Amin
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersson, Lars I.
    Hashemi, Mahdi
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Molecularly imprinted polymer in microextraction by packed sorbent for the simultaneous determination of local anesthetics: lidocaine, ropivacaine, mepivacaine and bupivacaine in plasma and urine samples2013In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 27, no 11, p. 1418-1488Article in journal (Refereed)
    Abstract [en]

    This study presents the use of molecularly imprinted polymer (MIP) as packing material for microextraction by packed syringe (MEPS) to achieve higher extraction selectivity. Pentycaine was used as template for MIP. Development and validation of the determination of lidocaine, ropivacaine, mepivacaine and bupivacaine in human plasma and urine samples utilizing MIP-MEPS and liquid chromatography–tandem mass spectrometry (LC-MS/MS) were carried out. The MEPS MIP-cartridge could be used for 100 extractions before it was discarded. The extraction recovery ranged from 60 to 80%. The correlation coefficients values were >0.999 for all assays using lidocaine, ropivacaine, mepivacaine and bupivacaine in the calibration range 5–2000 nmol/L. The accuracy of the studied compounds, given as a percentage variation from the nominal concentration values, ranged from -4.9 to 8.4% using plasma and urine samples. The between-batch precision, given as the relative standard deviation, at three different concentrations (quality control samples) was ranged from −4.7 to 14.0% and from 1.8 to 12.7% in plasma and urine, respectively. The lower limit of quantification and limit of detection of the studied substances were 5.0 and 1.0 nm, respectively

  • 5.
    Elmongy, Hatem
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Damanhour University, Egypt.
    Ahmed, Hytham
    Wahbi, Abdel-Aziz
    Amini, Ahmad
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Determination of metoprolol enantiomers in human plasma and saliva samples utilizing microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry2016In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 30, no 8, p. 1309-1317Article in journal (Refereed)
    Abstract [en]

    A sensitive, accurate and reliable bioanalytical method for the enantioselective determination of metoprolol in plasma and saliva samples utilizing liquid chromatography-electrospray ionization tandem mass spectrometry was developed and validated. Human plasma and saliva samples were pretreated by microextraction by packed sorbent (MEPS) prior to analysis. A new MEPS syringe form with two inputs was used. Metoprolol enantiomers and internal standard pentycaine (IS) were eluted from MEPS sorbent using isopropanol after removal of matrix interferences using aliquots of 5% methanol in water. Complete separation of metoprolol enantiomers was achieved on a Cellulose-SB column (150x4.6mm, 5m) using isocratic elution with mobile phase 0.1% ammonium hydroxide in hexane-isopropanol (80:20, v/v) with a flow rate of 0.8mL/min. A post-column solvent-assisted ionization was applied to enhance metoprolol ionization signal in positive mode monitoring (+ES) using 0.5% formic acid in isopropanol at a flow rate of 0.2mL/min. The total chromatographic run time was 10min for each injection. The detection of metoprolol in plasma and saliva samples was performed using triple quadrupole tandem mass spectrometer in +ES under the following mass transitions: m/z 268.0872.09 for metoprolol and m/z 303.3154.3 for IS. The linearity range was 2.5-500ng/mL for both R- and S-metoprolol in plasma and saliva. The limits of detection and quantitation for both enantiomers were 0.5 and 2.5ng/mL respectively, in both matrices (plasma and saliva). The intra- and inter-day precisions were presented in terms of RSD values for replicate analysis of quality control samples and were <5%; the accuracy of determinations varied from 96 to 99%. The method was able to determine the therapeutic levels of metoprolol enantiomers in both human plasma and saliva samples successfully, which can aid in therapeutic drug monitoring in clinical laboratories.

  • 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, p. 112-119Article in journal (Refereed)
    Abstract [en]

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

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

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

  • 8.
    Iadaresta, Francesco
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Crescenzi, Carlo
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Universita di Salerno, Italy.
    Amini, Ahmad
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Koyi, Hirsh
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Application of graphitic sorbent for online microextraction of drugs in human plasma samples2015In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1422, p. 34-42Article in journal (Refereed)
    Abstract [en]

    In the present work a new sorbent based on graphitized carbon (CarbonX (R) COA) was evaluated in microextraction by packed sorbent (MEPS) for extraction of lidocaine and ropivacaine from human plasma samples. The new graphitic sorbent showed high recoveries of lidocaine and ropivacaine compared to C18 sorbent In the present study the G-MEPS (syringe packed with graphitic sorbent) was connect online with liquid chromatography tandem mass spectrometry (LC-MS/MS). In order to obtain a fast and reliable method different factors affecting MEPS performance were investigated. The extraction efficiency of the graphitic sorbent was compared with silica-based sorbents used in MEPS. The G-MEPS was also evaluated for reuse (50-100 times). The recoveries of lidocaine and ropivacaine from plasma samples were 79% and 82%; respectively. The method was validated according to FDA (Food and Drug Administration) guideline for bioanalytical method validation. Linearity was assessed in the range 5-2000 nmol/L, with coefficient of determination r(2) > 0,995 (n=3) for lidocaine and r(2) > 0.997 (n=3) for ropivacaine. The lower limit of quantification (LLOQ) was 5 nmol/L and the limit of detection (LOD) was 1 nmol/L for studied analytes in plasma samples. For both analytes considered in this study the accuracy values in plasma samples were ranged from 86% to 113%. The Inter-day precisions, expressed as relative standard deviation (%RSD), at three different concentrations (QC-samples) ranged from 8% to 9% for lidocaine, and from 4% to 11% for ropivacaine.

  • 9.
    Isetun, Sindra
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of solid-phase microextraction with PDMS for air sampling of gaseous organophosphate flame-retardants and plasticizers2004In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 380, no 2, p. 319-324Article in journal (Refereed)
    Abstract [en]

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

  • 10.
    Larson, Tuula
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    An automated multidimensional preparative gas chromatographic system for isolation and enrichment of trace amounts of xenon from ambient air2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 400, no 2, p. 449-458Article in journal (Refereed)
    Abstract [en]

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

  • 11.
    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.

  • 12.
    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)
  • 13.
    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.

     

  • 14.
    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.

  • 15.
    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)
  • 16.
    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.

  • 17.
    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.))
  • 18. 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.

  • 19.
    Thewalim, Yasar
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Aldaeus, Fredrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Retention time prediction of compounds in Grob standard mixture for apolar capillary columns in temperature-programmed gas chromatography2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 393, no 1, p. 327-334Article in journal (Refereed)
    Abstract [en]

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

  • 20.
    Thewalim, Yasar
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bruno, Oscar
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Study of the chromatographic behaviour of selected alcohols and amines2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 3, p. 1335-1345Article in journal (Refereed)
    Abstract [en]

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

  • 21.
    Thewalim, Yasar
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Comparing columns for gas chromatography with the two-parameter model for retention prediction2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 31, p. 5305-5310Article in journal (Refereed)
    Abstract [en]

    The retention times of selected compounds in temperature programmed gas chromatography were predicted using a two-parameter model, on the basis of thermodynamic data obtained from isothermal runs on seven capillary columns, primarily substituted with 5% diphenylsiloxane. The scope for using thermodynamic data obtained from isothermal runs on one column to optimize separation on a different column or a different instrument setup was investigated. Additionally, the predictive utility of thermodynamic data obtained using a DB-5 column that had been in use for three years was compared to that of a new column of the same model. It was found that satisfactory separation could be achieved on one capillary column or instrument setup on the basis of thermodynamic data obtained using a different column or instrument set-up.

  • 22.
    Tollbäck, Johanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Isetun, Sindra
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic non-equilibrium SPME combined with GC, PICI, and ion trap MS for determination of organophosphate esters in air2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 396, no 2, p. 839-844Article in journal (Refereed)
    Abstract [en]

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

1 - 22 of 22
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