| 1. |
- Ahrens, Lutz, et al.
(författare)
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Characterization of five passive sampling devices for monitoring of pesticides in water
- 2015
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1405, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Five different passive sampler devices were characterized under laboratory conditions for measurement of 124 legacy and current used pesticides in water. In addition, passive sampler derived time-weighted average (TWA) concentrations were compared to time-integrated active sampling in the field. Sampling rates (R-S) and passive sampler-water partition coefficients (K-PW) were calculated for individual pesticides using silicone rubber (SR), polar organic chemical integrative sampler (POCIS)-A, POCIS-B, Chemcatcher (R) SDB-RPS and Chemcatcher (R) C-18. The median R-S (Lday(-1)) decreased as follows: SR (0.86) > POCIS-B (0.22) > POCIS-A (0.18) > Chemcatcher (R) SDB-RPS (0.05) > Chemcatcher (R) C-18 (0.02), while the median logK(PW) (Lkg(-1)) decreased as follows: POCIS-B (4.78)> POCIS-A (4.56) > Chemcatcher (R) SDB-RPS (3.17) >SR (3.14)> Chemcatcher (R) C-18 (2.71). The uptake of the selected compounds depended on their physicochemical properties, i.e. SR showed a better uptake for more hydrophobic compounds (log octanol-water partition coefficient (K-OW) > 5.3), whereas POCIS-A, POCIS-B and Chemcatcher (R) SDB-RPS were more suitable for hydrophilic compounds (logK(OW) < 0.70). Overall, the comparison between passive sampler and time-integrated active sampler concentrations showed a good agreement and the tested passive samplers were suitable for capturing compounds with a wide range of K-OW's in water. (C) 2015 Elsevier B.V. All rights reserved.
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| 2. |
- Azadmard-Damirchi, Sodeif, et al.
(författare)
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A single step solid-phase extraction method for complete separation of sterol oxidation products in food lipids
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1216, s. 36-42
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Tidskriftsartikel (refereegranskat)abstract
- One of the crucial steps in determination of sterol oxidation products (SOPs) in foods is their enrichment and purifications by various preparative methods for further analysis by GC and GC-MS. Among the preparative methods, SPE of various adsorbents and solvent systems, are being used most widely. At present, no single step SPE method is suitable to completely separate the SOPs. In this study, a SPE (I g silica) method, suitable for both transesterified and cold saponified oil samples. was developed to separate completely SOPs from other lipid components. This method resulted in high recovery from rapeseed oil of added 5 beta,6 beta-epoxycholestan-3 beta-ol (94-96%), cholest-5-en-3 beta-ol-7-one(94%), cholestane-3 beta,5 alpha,6 beta-triol (88-91%), cholest-5-en-3 beta,7 alpha-diol and 5 alpha,6 alpha-epoxycholestan-3 beta-ol (88-90%). The method has a high sample capacity of up to I g transesterified or cold-saponified oil sample. The method was tested and applied to different vegetable oils and to monitor the effects of refining processes on POPs in hazelnut oil. (C) 2008 Elsevier B.V. All rights reserved.
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| 3. |
- 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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| 4. |
- Do, Lan, et al.
(författare)
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Multivariate data analysis to characterize gas chromatography columns for dioxin analysis
- 2014
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1347, s. 137-145
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Tidskriftsartikel (refereegranskat)abstract
- Principal component analysis (PCA) was applied for evaluating the selectivity of 22 GC columns for which complete retention data were available for the 136 tetra- to octa-chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Because the hepta- and octa-homologues are easy to separate the PCA was focused on the 128 tetra- to hexa-CDD/Fs. The analysis showed that 21 of the 22 GC columns could be subdivided into four groups with different selectivity. Group I consists of columns with non-polar thermally stable phases (Restek 5Sil MS and Dioxin 2, SGE BPX-DXN, Supelco Equity-5, and Agilent DB-1, DB-5, DB-5ms, VF-5ms, VF-Xms and DB-XLB). Group II includes ionic liquid columns (Supelco SLB-IL61, SLB-IL111 and SLB-IL76) with very high polarity. Group III includes columns with high-percentage phenyl and cyanopropyl phases (Agilent DB-17 and DB-225, Quadrex CPS-1, Supelco SP-2331, and Agilent CP-Sil 88), and Group IV columns with shape selectivity (Dionex SB-Smectic and Restek LC-50, Supelco beta DEXcst, Agilent VF-Xms and DB-XLB). Thus, two columns appeared in both Group I and IV (Agilent VF-Xms and DB-XLB). The selectivity of the other column, Agilent DB-210, differs from those of these four groups. Partial least squares (PLS) regression was used to correlate the retention times of the tetra- to hexa-CDD/Fs on the 22 stationary phases with a set of physicochemical and structural descriptors to identify parameters that significantly influence the solute-stationary phase interactions. The most influential physicochemical parameters for the interaction were associated with molecular size (as reflects in the total energy, electron energy, core-core repulsion and standard entropy), solubility (aqueous solubility and n-octanol/water partition coefficient), charge distribution (molecular polarizability and dipolar moment), and reactivity (relative Gibbs free energy); and the most influential structural descriptors were related to these parameters, in particular, size and dipolar moment. Finally, the PCA and PLS analyses were complemented with linear regression analysis to identify the most orthogonal column combinations, which could be used in comprehensive two-dimensional gas chromatography (GC x GC) to enhance PCDD/F separation and congener profiling. (C) 2014 Elsevier B.V. All rights reserved.
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| 5. |
- Gustavsson, Jakob, et al.
(författare)
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Development and comparison of gas chromatography-mass spectrometry techniques for analysis of flame retardants
- 2017
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1481, s. 116-126
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Tidskriftsartikel (refereegranskat)abstract
- The restrictions on the use of legacy flame retardants (FRs) have increased the need of alternative FRs to comply with fire safety legislations. In this study, the feasibility of three different gas chromatography mass spectrometry (GC MS) techniques were investigated for the analysis of 102 legacy and alternative FRs including polybrominated diphenyl ethers (PBDEs, n =27), halogenated FRs (HFRs, containing bromine and/or chlorine, n = 46), and organophosphorous FRs (OPFRs, n = 29). The tested techniques included GC-single MS with (i) electon impact (EI) ionization and (ii) negative chemical ionization (NCI), and (iii) GC-tandem MS (MS/MS) with EI ionization. Out of the tested FRs, 90 could be detected under the used conditions on at least one of the three instrument setups. Later experiments included a selection of these FRs. For the majority of tested PBDEs (5 out of 6) and HFRs (24 out of 26), El-MS/MS provided the highest detectability (i.e. the lowest detection limits), while for most tested OPFRs (8 out of 13), El-MS performed better. The influence of matrix components on the analysis of FRs (n = 45) was investigated by analyzing a fortified surface water sample with the technique with the lowest selectivity, El-MS. Both peak enhancement and suppression were observed, and significant correlations between matrix effects and several physico-chemical properties (e.g., retention time and boiling point) were found for PBDEs. In a separate clean-up experiment using natural water spiked with legacy and alternative FRs (n = 30), alumina provided the highest mean recovery (90%) in comparison to acidified silica (67%) and Florisil (78%). This study provides new knowledge on analysis of FRs including a wide range of alternative FRs, and it will aid in the efforts of FR monitoring in the environment. (C) 2016 Elsevier B.V. All rights reserved.
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| 6. |
- Gustavsson, Jakob, et al.
(författare)
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Influence of natural organic matter on the extraction efficiency of flame retardants from surface waters
- 2017
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1524, s. 74-86
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Tidskriftsartikel (refereegranskat)abstract
- The influence of natural organic matter (NOM) on the solid-phase extraction (SPE) efficiency was investigated for legacy and emerging flame retardants (FRs; n =26) in surface water. Three different groups of FRs were analyzed: polybrominated diphenyl ethers (PBDEs), halogenated flame retardants (HFRs), and organophosphorus flame retardants (OPFRs). In addition, five sorbents (Amberlite XAD-2, Amberlite IRA-743, Oasis HLB, Chromabond HR-P, and Chromabond HR-X) were evaluated for the extraction of FRs (n=33) in water, of which Oasis HLB eluted with dichloromethane and acetone:n-hexane (1:1, v/v) provided the highest overall recoveries. In subsequent NOM experiments, where FRs were extracted from water containing different NOM concentrations, both increased and decreased extraction efficiency with increasing NOM level were observed. Physicochemical and semi-empirical quantum chemistry properties were calculated for the FRs and used for analyzing relations between FRs. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed that the FRs separated into four different groups based on their properties. The FRs within each group responded similarly to increasing NOM, while differences in behavior were observed between the groups. This suggests that the structural properties of micropollutants highly influence NOM-FR interaction mechanisms. For instance, at high NOM levels, recoveries decreased substantially for FRs containing a moiety that can form strong hydrogen bonds (such as the double-bonded oxygen in e.g., OPFRs). Many of the compounds showed maximum extraction efficiency at higher levels of NOM. This suggests that binding of NOM to the sorbent and subsequent interaction between sorbent-bound NOM and FRs is an important mechanism for extraction of micropollutants from surface waters. (C) 2017 Elsevier B.V. All rights reserved.
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| 7. |
- Persson, Ingmar
(författare)
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A low transition temperature mixture for the dispersive liquid-liquid microextraction of pesticides from surface waters
- 2019
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1605
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Tidskriftsartikel (refereegranskat)abstract
- This paper illustrates the development of a procedure based on the use of a low transition temperature mixture (LTTM) for the dispersive liquid-liquid microextraction (DLLME) of fungicides, insecticides and acaricides from surface waters. The LTTM preparation involves the heat-mixing of choline chloride and acetylsalicylic acid in a molar ratio 1:2 (ChCl(ASA)(2)). The resulting mixture appears as a clear viscous liquid at room-temperature, denser than water (1.20 +/- 0.01 g mL(-1)). For its characterization, differential scanning calorimetry (DSC) provided crucial evidence to classify it as a LTTM rather than as a deep eutectic solvent (DES) since it revealed an intense glass transition at -37 degrees C. Large-angle X-ray scattering (LAXS) confirmed the lack of any long-distance order. Due to the LTTM immiscibility with water, an evaluation study was carried out to test ChCl(ASA)(2) as an effective alternative to the conventional chlorinated solvents for DLLME. To this end, 24 pesticides were used as model compounds, extracted from surface water samples (5 mL) and analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The definitive procedure required the optimization of some key parameters such as volume of extracting solvent, type and volume of dispersing solvent, volume of the aqueous sample, LTTM dispersion procedure, and extraction time. Depending on pKa and logP values, recoveries ranged from 18 (for very polar compounds) to 96%, revealing that the ideal candidates for the extraction with ChCl(ASA)(2) are neutral compounds with logP >2. After complete validation, the method was applied to analyze water samples from the River Tiber where dodine and dimetomorph were found at low mu g L-1 concentration levels. (C) 2019 Elsevier B.V. All rights reserved.
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| 8. |
- Postigo, Cristina
(författare)
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A fully automated approach for the analysis of 37 psychoactive substances in raw wastewater based on on-line solid phase extraction-liquid chromatography-tandem mass spectrometry
- 2018
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1576, s. 80-89
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a multi-residue method for the simultaneous determination of 37 legal and illicit psychoactive substances in wastewater, including the most common illicit drugs (cocaine-related compounds, amphetamine-type stimulants, hallucinogens, opiates/opioids, and cannabinoids), new psychoactive substances (two synthetic cathinones, the synthetic opioid AH-7921, and the arylcyclohexylamine methoxetamine), and legal but controlled psychoactive substances (stimulants, benzodiazepines, antidepressants, sedatives, antipsychotics, and hypnotics). To this end a fully automated analytical approach based on solid phase extraction coupled in series to liquid chromatography tandem mass spectrometry detection (on-line SPE- LC-MS/MS) was used. The methodology developed was validated in terms of linearity, recovery, repeatability, and sensitivity in wastewater. Method linearity was between 0.1 ng/L (or the analyte limit of quantification if higher) and 2,000 ng/L (10,250 ng/L in the case of caffeine). Absolute recoveries were variable (between 5% and 132%), depending on the analyte. However, the use of isotopically labeled compounds corrected for analyte losses during the extraction process and matrix effects (relative recoveries within the range of 80-120%). Repeatability of the method was satisfactory for all analytes, with RSD values lower than 13% for most compounds. Limits of detection and quantification in wastewater were below 7 and 23 ng/L, respectively, for all analytes except lormetazepam (10 and 32 ng/L), caffeine (13 and 44 ng/L), and the cannabinoids 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (18 and 61 ng/L) and 11-hydroxy-Delta(9)- tetrahydrocannabinol (69 and 228 ng/L). The method was applied to the analysis of wastewater samples collected daily in Barcelona for one week. Twenty-five of the 37 analytes were detected in the samples analyzed. Average concentrations ranged from 7 ng/L in the case of zolpidem to 54 mu g/L in the case of caffeine. (C) 2018 Elsevier B.V. All rights reserved.
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| 9. |
- Sörengård, Mattias, et al.
(författare)
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Losses of poly- and perfluoroalkyl substances to syringe filter materials
- 2020
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1609
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Tidskriftsartikel (refereegranskat)abstract
- Syringe filters are used to separate solids from liquids prior to analysis of poly- and perfluoroalkyl substances (PFASs). This is a critical step in sample preparation, as losses of PFASs to the filter material can be significant and lead to underestimation. This study evaluated losses of 21 PFASs in three different matrices (methanol, MilliQ water, and water containing 10 mg L-1 dissolved organic carbon (DOC)) to six different types of syringe filter (0.45 and 0.22 mu m). Regarding sample matrix, the lowest average Sigma(21) PFAS losses were observed in methanol (13%), followed by DOC water (19%) and MilliQ water (26%). Regarding syringe filter material, the lowest average losses of Sigma(21) PFAS in DOC water and MilliQ water were observed for a recycled cellulose filter (average losses 16% and 21%, respectively), while a polypropylene filter had the lowest Sigma(21) PFAS losses in methanol (9%). A smaller polyethersulfone (PES) filter (0.22 mu m, 17 mm empty set) showed significantly (p < 0.05) lower Sigma(21) PFAS losses in DOC water (on average 7.3%) than a larger PES filter (0.45 mu m, 37 mm empty set) (23%). In DOC water, losses to the filter increased by 3.8%, 5.1%, and 8.4% per CF2-moiety for C-3-C-11 perfluoroalkyl carboxylates (PFCAs), perfluoroalkyl sulfonates (PFSAs), and fluorotelomer sulfonic acids (FTSAs), respectively. Comparing different functional groups of PFASs, losses increased as follows: PFCAs < PFSAs < FTSAs < perfluorooctanesulfonamides (FOSAs). Thus, care is needed when including filtration in PFAS analysis, since losses can be significant (up to 100%) depending on the type of syringe filter, target PFAS, and matrix. (C) 2019 Elsevier B.V. All rights reserved.
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| 10. |
- Yong, Jean W.H
(författare)
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Simultaneous extraction, separation, isolation and identification of endogenous components from Etlingera elatior by pressurized matrix solid-phase dispersion using liquid chromatography-mass spectrometry
- 2020
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1611
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Tidskriftsartikel (refereegranskat)abstract
- From the analytical chemistry point-of-view, an ideal sample preparation method should be simple, rapid, automatic, selective, precise, exhaustive, reproducible and protect the analyte-of-interest from degradation. In this study, a novel sample preparation method, named pressurized matrix solid-phase dispersion (p-MSPD) extraction was developed for simultaneously extracting, separating, purifying, isolating, and analyzing endogenous components in a solid sample matrix. Etlingera elatior, a traditional medicinal plant known as the torch ginger, was applied as a sample matrix to evaluate the p-MSPD process. The entire extraction, separation, isolation, fractionation and detection were performed automatically with a commercial LC-MS system. The novel method was satisfactorily applied for the preparation of real samples without optimization, which had the ability to selectively isolate pure compounds from the solid sample matrix for further NMR analysis. Therefore, the method is recommended for quality control of traditional medicines, research efforts when sample amounts are limited, and laboratories that have ordinary LC-MS instrumentation. (C) 2019 Elsevier B.V. All rights reserved.
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