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| 2. |
- Sandahl, Margareta, et al.
(författare)
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On-line automated sample preparation for liquid chromatography using parallel supported liquid membrane extraction and microporous membrane liquid-liquid extraction
- 2002
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 975:1, s. 211-217
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Tidskriftsartikel (refereegranskat)abstract
- An automated system was developed for analysis of non-polar and polar ionisable compounds at trace levels in natural water. Sample work-up was performed in a flow system using two parallel membrane extraction units. This system was connected on-line to a reversed-phase HPLC system for final determination. One of the membrane units was used for supported liquid membrane (SLM) extraction, which is suitable for ionisable or permanently charged compounds. The other unit was used for microporous membrane liquid-liquid extraction (MMLLE) suitable for uncharged compounds. The fungicide thiophanate methyl and its polar metabolites carbendazim and 2-aminobenzimidazole were used as model compounds. The whole system was controlled by means of four syringe pumps. While extracting one part of the sample using the SLM technique, the extract from the MMLLE extraction was analysed and vice versa. This gave a total analysis time of 63 min for each sample resulting in a sample throughput of 22 samples per 24 h. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
- Barri, Thaer, et al.
(författare)
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Advances and developments in membrane extraction for gas chromatography: Techniques and applications.
- 2008
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1186:1-2, s. 16-38
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Barri, Thaer, et al.
(författare)
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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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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1111:1, s. 11-20
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Berhanu, Tarekegn, et al.
(författare)
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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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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1103:1, s. 1-8
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Chimuka, Luke, et al.
(författare)
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Selective extraction of triazine herbicides based on a combination of membrane assisted solvent extraction and molecularly imprinted solid phase extraction
- 2011
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1218:5, s. 647-653
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Tidskriftsartikel (refereegranskat)abstract
- A selective extraction technique based on the combination of membrane assisted solvent extraction and molecularly imprinted solid phase extraction for triazine herbicides in food samples was developed. Simazine, atrazine, prometon, terbumeton, terbuthylazine and prometryn were extracted from aqueous food samples into a hydrophobic polypropylene membrane bag containing 1000 mu L of toluene as the acceptor phase along with 100 mg of MIP particles. In the acceptor phase, the compounds were re-extracted onto MIP particles. The extraction technique was optimised for the type of organic acceptor solvent, amount of molecularly imprinted polymers particles in the organic acceptor phase, extraction time and addition of salt. Toluene as the acceptor phase was found to give higher triazine binding onto MIP particles compared to hexane and cyclohexane. Extraction time of 120 min and 100 mg of MIP were found to be optimum parameters. Addition of salt increased the extraction efficiency for more polar triazines. The selectivity of the technique was demonstrated by extracting spiked cow pea and corn extracts where clean chromatograms were obtained compared to only membrane assisted solvent extraction or only molecularly imprinted solid phase extraction. The study revealed that this combination may be a simple way of selectively extracting compounds in complex samples. (C) 2010 Elsevier B.V. All rights reserved.
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| 7. |
- Fontanals, Nuria, et al.
(författare)
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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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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1133:1-2, s. 41-48
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Hyder, Murtaza, et al.
(författare)
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Hollow-fiber liquid phase microextraction for lignin pyrolysis acids in aerosol samples and gas chromatography-mass spectrometry analysis.
- 2012
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Ingår i: Journal of chromatography. A. - : Elsevier BV. - 1873-3778 .- 0021-9673. ; 1249, s. 48-53
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Tidskriftsartikel (refereegranskat)abstract
- A method based on three-phase hollow fiber liquid phase microextraction was developed and successfully applied to aerosols for the analysis of lignin pyrolysis acids such as syringic acid, vanillic acid and p-salicylic acid. Important parameters related to extraction process like organic solvent for membrane phase, tri-n-octylphosphine (TOPO) oxide contents in organic solvent, stirring speed, extraction time etc. were optimized. 6-Undecanone with 15% TOPO contents (w/v) was found a suitable solvent for organic liquid membrane, 900rpm was the optimum stirring speed and time of 4h was found optimum extraction time. Donor phase pH was 1.3 while acceptor phase pH was adjusted to 9.5. The optimized extraction method was used for the extraction of real aerosol samples. Analytes were derivatized using BSTFA containing 1% trimethylsilyl chloride and gas chromatography mass spectrometry was used for analysis. Very low limits of detection in the range 0.2-1.0ngL(-1) were found, corresponding to 10-50pgm(-3) of analytes in aerosols. Extraction efficiency obtained ranged 60.3-71.7% and enrichment factors ranged 3015-3585 times. The optimized method was successfully applied to aerosol samples and all of the selected analytes were detected in the analyzed samples.
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| 9. |
- Lezamiz, Jon, et al.
(författare)
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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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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1152:1-2, s. 226-233
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Liu, Jing-fu, et al.
(författare)
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Disposable ionic liquid coating for headspace solid-phase microextraction of benzene, toluene, ethylbenzene. and xylenes in paints followed by gas chromatography-flame ionization detection
- 2005
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1066:1-2, s. 27-32
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Tidskriftsartikel (refereegranskat)abstract
- Solid-phase microextraction (SPME) with a disposable ionic liquid (IL) coating was developed for headspace extraction of benzene, toluene, ethylbenzene, and xylenes (BTEX) in paints. The SPME fiber was coated with IL prior to every extraction, then the analytes were extracted and desorbed on the injection port of gas chromatography, and finally the IL coating on the fiber was washed out with solvents. The coating and washing out of IL from the fiber can be finished in a few minutes. This disposable IL-coated fiber was applied to determine BTEX in water-soluble paints with results in good agreement with that obtained by using commercially available SPME fibers. For all the four studied paints samples, the benzene contents were under the detection limits, but relatively high contents of toluene, ethylbenzene and xylenes (56-271 mug g(-1)) were detected with spiked recoveries in the range of 70-114%. Compared to the widely used commercially available SPME fibers, this proposed disposable IL-coated fiber has much lower cost per determination, comparable reproducibility (RSD < 11%), and no carryover between each determination. Considering that IL possess good extractability for various organic compounds and metals ions, and that task-specific IL can be designed and synthesized for selective extraction of target analytes, this disposable IL coating SPME might has great potential in sample preparation. (C) 2005 Elsevier B.V. All rights reserved.
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