| 1. |
- Barri, Thaer, et al.
(author)
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Advances and developments in membrane extraction for gas chromatography: Techniques and applications.
- 2008
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1186:1-2, s. 16-38
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Journal article (peer-reviewed)abstract
- This review article focuses on advances and technical developments of the realm of membrane extraction techniques for the analytes that are (made) amenable to gas chromatographic analysis, and sheds light on the analytical applications to biological and environmental samples. In this review, the state of the art in this growing area of membrane extraction for gas chromatography is presented and several selected examples from our work and that of other groups are discussed. The published articles on the techniques and their applications, found in the scientific literature between the years 2000 and May 2007 and cited in over than 100 references, are perused and commented. A good deal of light will be thrown on the novelty of the techniques, instrumentations and applications. The mentioned techniques are mainly microporous membrane liquid-liquid extraction, extracting syringe, two-phase hollow-fibre-protected liquid-phase microextraction and its modifications, and membrane extraction with sorbent interface and its variants. The merits and demerits of the techniques will be highlighted.
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| 2. |
- Barri, Thaer, et al.
(author)
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Extracting Syringe for determination of organochlorine pesticides in leachate water and soil-water slurry: A novel technology for environmental analysis
- 2006
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1111:1, s. 11-20
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Journal article (peer-reviewed)abstract
- The Extracting Syringe (ESy), a novel membrane-based sample preparation technique directly coupled as an autosampler to gas chromatography, has been employed for the analysis of organochlorine pesticides (OCPs) in raw leachate water. The ESy has also been applied for extraction of OCPs from contaminated soil samples and its performance has been compared to liquid-solid extraction (LSE) and accelerated solvent extraction (ASE). Extraction of 3-mL leachate sample at the optimised conditions resulted in enrichment factors from 32 (Endrin aldehyde) to 242 (Endrin) and detection limits from 1 to 20 ng/L. The inter-day and intra-day repeatability (% RSD) at 100 and 500 ng/L were < 6% and < 24%, respectively. The relative recovery at 100 and 500 ng/L ranged from 68% (Aldrin) to 116% (Endrin aldehyde); except Heptachlor that showed 51 and 60%, respectively. The ESy extraction of the slurry-made soil samples revealed occurrence of Endosulfan I (18.2 mu g/g soil), 4,4'-DDE (2.6 ng/g soil), Endosulfan 11 (8.7 mu g/g soil) and Endosulfan sulfate (1.1 mu g/g soil); showing good agreement with LSE results. The total ESy consumption of organic solvents was 4.2 mL from which only 0.6 mL n-undecane was used during the extraction step (7 mu L for the extraction per se), while in the LSE and ASE, it was 420 and 18.1 mL, respectively. The ESy extraction time (0.5 h) was comparable to the ASE time (0.6 h); and the time required for the LSE was 3.75 h. To sum up, the ESy has shown its competency to LSE and ASE technologies, demonstrating its applicability for environmental analysis of organic pollutants, towards green techniques for green environment. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Bergström, Staffan, et al.
(author)
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Extracting syringe for extraction of phthalate esters in aqueous environmental samples
- 2007
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In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 594:2, s. 240-247
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Journal article (peer-reviewed)abstract
- The use of the extracting syringe (ESy), a fully automated membrane-based extraction technique, for analysis of phthalate esters in complex aqueous samples has been investigated. The ESy, working as an autosampler that combines the extraction process and injection into the gas chromatograph (GC) in one single step, is placed on top of the GC equipped with a flame ionisation detector. The aqueous samples are loaded in a tray and automatically extracted by employing microporous membrane liquid-liquid extraction principle. After the extraction, the extract is directly injected into the GC's programmable temperature vaporisation injector. Six different phthalate esters were used as model compounds. Four extraction solvents were tested and the addition of sample organic modifier was examined. Toluene was the optimal solvent to use for extraction. Due to the large variation in polarity of phthalate esters, 50% methanol as organic modifier had to be added to the samples so as to extract the most nonpolar phthalate esters; di-2-ethylhexylphthalate and di-n-octylphthalate, whereas the other four relatively polar phthalate esters were extracted from unmodified samples. No significant difference between extraction of river water, leachate water from a landfill and reagent water was noted, except for minor deviations. The extraction time was 20 min for extraction of a 1-mL sample, resulting in a good linearity for all aqueous media investigated, good enrichment factors (54-110 folds) and low LOD values (0.2-10 ng mL(-1)) and relative standard deviation (%R.S.D.; 0.9-3.7%).
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| 4. |
- Berhanu, Tarekegn, et al.
(author)
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Determination of trace levels of dinitrophenolic compounds in environmental water samples using hollow fiber supported liquid membrane extraction and high performance liquid chromatography
- 2006
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1103:1, s. 1-8
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Journal article (peer-reviewed)abstract
- A hollow fiber supported liquid membrane extraction method for the liquid chromatographic determination of dinitrophenolic compounds at ppt levels has been developed. Different variables affecting the extraction process, such as extraction time, shaking speed, acceptor pH, acceptor buffer concentration, salt content and humic acids have been studied. Enrichment factors up to 7000 times were obtained. Validation of the method included calibration experiments and studies of the linearity of the responses in different matrices. Good linearity was obtained in the environmental matrices evaluated. Detection limits range from 6.0 to 8.0 ng/L, and the relative standard deviations do not exceed 7% in terms of repeatability. (c) 2005 Elsevier B.V. All rights reserved.
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| 5. |
- Fontanals, Nuria, et al.
(author)
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Determination of polybrominated diphenyl ethers at trace levels in environmental waters using hollow-fiber microporous membrane liquid-liquid extraction and gas chromatography-mass spectrometry
- 2006
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1133:1-2, s. 41-48
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Journal article (peer-reviewed)abstract
- In this study, we present a simple and easy-to-use extraction method that is based on a hollow-fiber microporous membrane liquid-liquid extraction (HF-MMLLE), as an extraction technique, followed by gas chromatography-mass spectrometry (GC-MS) to determine a group of brominated flame retardants (BFRs), polybrominated diphenyl ethers (PBDEs), at trace levels in aqueous samples. The hollow-fiber membrane (HF) filled with organic solvent was immersed into the aqueous sample, spiked with the analytes at ng l(-1) level, and stirred for 60 min. The proposed method could attain enrichment factors (E-e) up to 5200 times, after optimising parameters, such as organic solvent, stirring speed and extraction time, that affect the extraction. The HF-MMLLE-GC-MS method was successfully applied to the extraction of PBDEs from tap, river and leachate water samples with spike recoveries ranging from 85% to 110%. The method validation with reagent and leachate water samples provided good linearity, detection limits of 1.1 ng l(-1) or lower, both in reagent and leachate water, as well as satisfactory precision in terms of repeatability and reproducibility with values of % relative standard deviation (%RSD) lower than 8.6 and 16.9, respectively. (c) 2006 Elsevier B.V. All rights reserved.
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| 6. |
- Lezamiz, Jon, et al.
(author)
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Development of a simple hollow fibre supported liquid membrane extraction method to extract and preconcentrate dinitrophenols in environmental samples at ng L-1 level by liquid chromatography
- 2007
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1152:1-2, s. 226-233
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Journal article (peer-reviewed)abstract
- An easy and rapid hollow-fibre supported liquid membrane method (HFSLM) has been developed to extract and determinate the total concentration of four dinitrophenols in environmental water at ng L-1 level. This extraction method provides a high selectivity, short extraction time and very low cost for real samples. It is a three-phase system, aqueous-organic-aqueous, where the organic solvent is held into the fibre pores, being in contact with the two other phases. The organic phase is formed by two different organic solvents, with two different polarities, n-undecane and toluene (1: 1). The optimization step was performed using a three-variable Doehler design, involving three factors, stirring speed, fibre length and sample volume. The organic phase composition, as well as the pH of the acceptor and donor phases was also optimized. The extraction equilibrium was reached after 30 min, after which essentially the total amount (90-80%) of the four dinitrophenolic compounds were extracted from the sample. Better repeatability and reproducibility at the expense of lower enrichment factors was obtained compared with other methods, employing incomplete extraction during a fixed time. The matrix effect was tested by performing extractions from leachate water and river water. This method is linear in the range 0.1-100 mu g L-1 in different matrices, with detection limit around 100 ng L-1, after extraction of 6 mL of sample and using high performance liquid chromatography for final analysis. (C) 2006 Elsevier B.V. All rights reserved.
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