| 1. |
- Lim, Hwanmi, et al.
(författare)
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Benzo[a]pyrene-specific online high-performance liquid chromatography fractionation of air particulate extracts : a tool for evaluating biological interactions
- 2014
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Ingår i: Journal of Chromatography A. - Stockholm : Karolinska Institutet, Institute of Environmental Medicine. - 0021-9673 .- 1873-3778.
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Tidskriftsartikel (refereegranskat)abstract
- Benzo[a]pyrene (B[a]P) is a known human carcinogen and is commonly used as a surrogate for assessing the carcinogenic risk posed by complex mixtures of polycyclic aromatic hydrocarbons (PAHs) present in air particulate matter (PM). However, studies have shown that using B[a]P as a surrogate may underestimate the carcinogenic potential of PAH mixtures, as the risk assessment approach does not consider interaction effects. Thus, toxicological studies using B[a]P to assess its carcinogenic potential in environmentally derived complex mixtures, as opposed to single compound experiments, could improve risk assessment. The intention of the present study was to develop an online HPLC fractionation system for the selective removal of B[a]P from air PM extracts. Two serial pyrenylethyl (PYE) columns enabled selective separation of B[a]P from its isomers and other PAHs as well as a short fractionation cycle of 30min. One run consisted of three collection steps: the first fraction contained PAHs eluting earlier than B[a]P, the second contained B[a]P and the last contained later-eluting PAHs. The selectivity and recovery of the system was investigated using extracts of Stockholm air PM samples. The overall recovery for all PAHs was approximately 80%, and the system proved to be selective, as it removed 94% of B[a]P and less than 3% of benzo[b]fluoranthene from the complex PAH mixture. Exposing human cells to blanks generated by the fractionation system did not induce cytotoxicity or DNA damage signalling. In conclusion, the online HPLC system was selective for B[a]P fractionation whilst minimising run-to-run variation and allowing repeated fractionations for larger samples due to its relatively short run time.
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| 2. |
- Aldaeus, Fredrik, et al.
(författare)
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Multi-step dielectrophoresis for separation of particles
- 2006
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1131:1-2, s. 261-266
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Tidskriftsartikel (refereegranskat)abstract
- A new concept for separation of particles based on repetitive dielectrophoretic trapping and release in a flow system is proposed. Calculations using the finite element method have been performed to envision the particle behavior and the separation effectiveness of the proposed method. As a model system, polystyrene beads in deionized water and a micro-flow channel with arrays of interdigited electrodes have been used. Results show that the resolution increases as a direct function of the number of trap-and-release steps, and that a difference in size will have a larger influence on the separation than a difference in other dielectrophoretic properties. About 200 trap-and-release steps would be required to separate particles with a size difference of 0.2%. The enhanced separation power of dielectrophoresis with multiple steps could be of great importance, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity, or for separations based on combinations of difference in size and dielectric properties.
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| 3. |
- Aldaeus, Fredrik, et al.
(författare)
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Prediction of retention times and peak widths in temperature-programmed gas chromatography using the finite element method
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1216:1, s. 134-139
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Avagyan, Rozanna, et al.
(författare)
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Determination of benzothiazole and benzotriazole derivates in tire and clothing textile samples by high performance liquid chromatography-electrospray ionization tandem mass spectrometry
- 2013
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1307, s. 119-125
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Tidskriftsartikel (refereegranskat)abstract
- A high performance liquid chromatography–tandem mass spectrometry method utilizing electrospray ionization in positive and negative mode has been developed for the separation and detection of benzothiazole and benzotriazole derivates. Ultra-sonication assisted solvent extraction of these compounds has also been developed and the overall method demonstrated on a selected clothing textile and an automobile tire sample. Matrix effects and extraction recoveries, as well as linearity and limits of detection have been evaluated. The calibration curves spanned over more than two orders of magnitude with coefficients of correlation R2 > 0.99 and the limits of detection and the limits of quantification were in the range 1.7–58 pg injected and 18–140 pg/g, respectively. The extraction recoveries ranged between 69% and 102% and the matrix effects between 75% and 101%. Benzothiazole and benzotriazole derivates were determined in the textile sample and benzothiazole derivatives determined in the tire sample with good analytical performance.
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| 5. |
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| 6. |
- Brits, Martin, et al.
(författare)
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Comprehensive two-dimensional gas chromatography coupled to high resolution time-of-flight mass spectrometry for screening of organohalogenated compounds in cat hair
- 2018
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1536, s. 151-162
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Tidskriftsartikel (refereegranskat)abstract
- The coupling of comprehensive two-dimensional gas chromatography with high-resolution time of-flight mass spectrometry offers the best separation efficiency combined with accurate mass measurements over a wide mass range. The tremendous power of this screening tool is illustrated by trace qualitative screening analysis of organohalogenated compounds (OHCs) in pet cat hair. Tentative identification was supported by mass spectral database searches and elemental formula prediction from the experimentally determined accurate mass data. This screening approach resulted in the first tentative identification of pentabromoethylbenzene, decabromodiphenyl ethane, hexabromocyclododecane, trisbromoneopentyl alcohol, tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl)phosphate in the South African indoor environment. A total of seventy-two OHCs were identified in the samples and include known flame retardants, such as polybrominated diphenyl ethers, and legacy contaminants such as polychlorinated biphenyls and organochlorine, organophosphorous and pyrethroid pesticides. The results obtained from cat hair indicate that these pets are exposed to complex mixtures of OHCs and the detection of these compounds suggests that non-invasive cat hair samples can be used to model indoor exposure with reference to external deposition of OHCs present in the air and dust surrounding people. Toddlers share the same environment as pet cats and therefore also the same health risks.
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| 7. |
- Carrizo, Daniel, et al.
(författare)
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Gas chromatographic-mass spectrometric analysis of polychlorostyrene congener mixtures in sediments, human sera and cord sera
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1216:30, s. 5723-5729
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Tidskriftsartikel (refereegranskat)abstract
- Complex mixtures of polychlorostyrenes are produced and released into the environment by reaction of chlorine with graphite at high temperatures, e.g. in electrodes. The occurrence of these compounds in the environment or human tissues is often indicative of pollution from electrolytic processes. Combined gas chromatography coupled to electron impact and negative ion chemical ionization mass spectrometry is described here for the analysis of these compounds in sediments, human venous sera and cord sera. This method has allowed a specific congener identification and quantification of the chlorostyrene mixtures present in fluvial sediments polluted by effluents from a chlorine-alkali plant. Besides octachlorostyrene, the mixture of compounds identified involved the six possible heptachlorostyrenes, fifteen hexachlorostyrenes and seven pentachlorostyrenes, having concentrations in the range of 76-16000 ng g(-1) dry weight. In human sera from the Population exposed to airborne emissions from this plant these compounds ranged between 17 and 63 ng L-1 and the distributions were dominated by octachlorostyrene, three heptachlorostyrenes, including beta,beta-2,3,4,5,6-heptachlorostyrene, and alpha-2,3,4,5,6-hexachlorostyrene. Both distribution patterns showed major differences in composition despite the common pollution source that was influencing both types of samples. The method also revealed qualitative differences between maternal and cord sera from the exposed population.
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| 8. |
- Elmongy, Hatem, et al.
(författare)
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Development and validation of a UHPLC-HRMS method for the simultaneous determination of the endogenous anabolic androgenic steroids in human serum
- 2020
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1613
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Tidskriftsartikel (refereegranskat)abstract
- Being performance enhancing hormones, endogenous anabolic androgenic steroids (EAAS) are banned from most competitive sports by the World Anti-doping Agency (WADA). In anti-doping control laboratories, routine assays are mainly performed on urine samples of athletes in and out of competitions. Serum constitutes a promising alternative to urine as it is less subjected to manipulation or contamination that may influence the method sensitivity. The simultaneous determination of EAAS including conjugated metabolites using LC-MS is very challenging due to their contradicting chemical behaviors at the ionization interface of the mass spectrometer. This may prejudice their detection or limit the method sensitivity. Herein, we have addressed these challenges and developed a new method for the simultaneous determination of unconjugated, sulphate- and glucuronide-conjugated EAAS (Androsterone, Etiocholanolone, testosterone, epitestosterone, dihydrotestosterone, dehydroepiandrosterone, androstenedione and 17a-hydroxyprogesterone) in human serum using ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS). The use of mass spectrometric detection in full scan mode facilitated the study of the most versatile adducts for detection and quantitation. A solid phase extraction method was developed for the sample preparation prior to analysis. The method limits of quantitation ranged from 0.006 to 7.904 ng/mL and the recoveries ranged from 70.2% to 96.5%. The method calibration was performed in untreated serum representing realistic matrix composition with correlation coeffecients ranged from 0.9859 to 0.9988. Finally, the serum-levels of the investigated steroids were determined in 4 male and 1 female human subjects to provide estimates of baseline levels based on individual values.
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| 9. |
- Elmongy, Hatem, et al.
(författare)
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Online post-column solvent assisted and direct solvent-assisted electrospray ionization for chiral analysis of propranolol enantiomers in plasma samples
- 2015
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1418, s. 110-118
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Tidskriftsartikel (refereegranskat)abstract
- An Online post-column solvent-assisted ionization (OPSAI) method was developed for enhancing the ionization of the beta-blocker propranolol utilizing normal phase LC-MS/MS. Solvent-assisted electrospray ionization (SAESI) was studied by the introduction of the assistant solvents A: 0.5% Formic acid in Isopropanolol, B: 0.5% Formic acid in lsopropanolol-Water (1:1), and C: 0.5% Formic acid in water into the electrospray ionization chamber using a spray needle. Analyte molecules can be directly ionized by the aid of the assistant solvent spray. Both methods were applied to the chiral separation of propranolol enantiomers using normal phase analysis on cellulose-based chiral column. Interestingly, both methods are easy to handle and offer a wide range of assistant solvents that can be used in order to gain the optimum ionization of the analyte molecules. The both methods considerably improved the analyte signal and the peak area greatly increased. The propranolol average signal-to-noise (S/N) ratio was enhanced from 26 +/- 1 and 42 +/- 1 to 2341 +/- 61 and 1725 +/- 29 for R-propranolol and S-propranolol, respectively, when the post-column solvent method (OPSAI) was used with isopropanol-assistant solvent (A). While in case of solvent-assisted electrospray ionization method (SAESI) signal was enhanced from 26 +/- 1 and 42 +/- 1 to 2223 +/- 72 and 2155 +/- 58 for R-propranolol and S-propranolol, respectively, with water as an assistant solvent. The limit of detection was 10 ng/mL and the method was linear in the range 50-2000 ng/mL. The NPLC-MS method was applied for the determination of propranolol enantiomers in human plasma after microextraction by packed C18 sorbent.
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| 10. |
- Gonzalez, Nelida J. D., et al.
(författare)
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New method for resolving the enantiomeric composition of 2-methyltetrols in atmospheric organic aerosols
- 2011
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1218:51, s. 9288-9294
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Tidskriftsartikel (refereegranskat)abstract
- In order to facilitate the determination of the primary and secondary origin of atmospheric organic aerosols, a novel method involving chiral capillary gas chromatography coupled with mass spectrometry has been developed and validated. The method was focused on the analysis of 2-methylerythritol and 2-methylthreitol, considered to be tracers of secondary organic aerosols from the oxidation of atmospheric isoprene. The method was validated by performing various tests using authentic standards, including pure enantiomeric standards. The result showed that the analytical method itself does not affect the enantiomeric composition of the samples analyzed. The method was applied on atmospheric aerosols from a boreal forest collected in Aspvreten, Sweden and on laboratory samples obtained from liquid phase oxidation of isoprene and smog chamber experiments. Aerosol samples contained one enantiomer of 2-methylerythritol in significantly larger quantities than the others. In contrast, the liquid-phase oxidation of isoprene and its gas-phase oxidation in the smog chamber produced all enantiomers in equal quantities. The results obtained where the enantiomer fraction, EF, is larger than 0.50 suggest that 2-methyltetrols in atmospheric aerosols may also have biological origin. Information about the differences between enantiomer fractions obtained using this method brings new insights in the area of atmospheric aerosols.
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