| 1. |
- 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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| 2. |
- 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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| 3. |
- Liu, Jing-fu, et al.
(författare)
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Passive extraction and clean-up of phenoxy acid herbicides in samples from a groundwater plume using hollow fiber supported liquid membranes
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1160:1-2, s. 56-63
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Tidskriftsartikel (refereegranskat)abstract
- Hollow fiber supported liquid membranes were applied for the passive extraction of phenoxy acid herbicides from water samples. Polypropylene hollow fiber membranes (240 mu m i.d., 30 mu m wall thickness, 0.05 mu m pore size, 30 cm length) were impregnated with 2.0% tri-n-octylphosphine oxide (TOPO) in di-n-hexyl ether in the pores of the fiber wall to form a liquid membrane. They were then filled with basic solution in the lumen as acceptor and finally placed into the sample (donor). Complete extraction of phenoxy acid herbicides including 2,4-D, MCPA, dichlorprop, and mecoprop from an acidified sample (4 mL, adjusted to pH 1.5 with HCl) into basic acceptor (10 mu L of 0.2 M NaOH) was achieved after 4 h of shaking (100 rpm) resulting in an enrichment factor of 400 times. The acceptor was then neutralized by addition of HCl and injected into a HPLC system for the determination of the phenoxy acid herbicides. Environmentally relevant salinity (0-3.5% NaCl) and dissolved organic matter (0-25 mg/L of dissolved organic carbon) had no significant effect on the extraction. The method provided extraction efficiencies of more than 91%, detection limits of 0.3-0.6 mu g/L, and combined extraction and clean up in one single step. This procedure was applied to deter-mine aqueous concentrations of phenoxy acid herbicides in groundwater samples collected from an old dumping site (Cheminova, Denmark) with detected concentrations up to 5800 mu g/L. Although the samples were very dirty with large amounts of suspended particles, non-aqueous phase liquids (NAPLs) and dissolved organic matters, good spike recoveries (80-126%) were obtained for 10 of the 11 samples. (c) 2007 Elsevier B.V. All rights reserved.
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| 4. |
- Tao, Yong, et al.
(författare)
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Hollow fiber supported ionic liquid membrane microextraction for determination of sulfonamides in environmental water samples by high-performance liquid chromatography
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1216:35, s. 6259-6266
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Tidskriftsartikel (refereegranskat)abstract
- By using ionic liquid as membrane liquid and tri-n-octylphosphine oxide (TOPO) as additive, hollow fiber supported liquid phase microextraction (HF-LPME) was developed for the determination of five sulfonamides in environmental water samples by high-performance liquid chromatography with ultraviolet detection The extraction solvent and the parameters affecting the extraction enrichment factor such as the type and amount of carrier, pH and volume ratio of donor phase and acceptor phase, extraction time, salt-out effect and matrix effect were optimized. Under the optimal extraction conditions (organic liquid membrane phase: [C8MIM][PF6] with 14% TOPO (w/v); donor phase: 4mL, pH 4.5 KH2PO4 with 2M Na2SO4; acceptor phase: 25microL, pH 13 NaOH; extraction time: 8 h), low detection limits (0.1-0.4microg/L, RSDor=0.999) were obtained for all the analytes. The presence of humic acid (0-25mg/L dissolved organic carbon) and bovine serum albumin (0-100 μg/mL) had no significant effect on the extraction efficiency. Good spike recoveries over the range of 82.2-103.2% were obtained when applying the proposed method on five real environmental water samples. These results indicated that this present method was very sensitive and reliable with good repeatabilities and excellent clean-up in water samples. The proposed method confirmed hollow fiber supported ionic liquid membrane based LPME to be robust to monitoring trace levels of sulfadiazine, sulfamerazine, sulfamethazine, sulfadimethoxine and sulfamethoxazole in aqueous samples.
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| 5. |
- Tao, Yong, et al.
(författare)
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Simultaneous conduction of two- and three-phase hollow-fiber-based liquid-phase microextraction for the determination of aromatic amines in environmental water samples
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1216:5, s. 756-762
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a simultaneously performed two-/three-phase hollow-fiber-based liquid-phase microextraction (HF-LPME) method for the determination of aromatic amines with a wide range of pKa (-4.25 to 4.6) and log KOW (0.9-2.8) values in environmental water samples. Analytes including aniline, 4-nitroaniline, 2,4-dinitroaniline and dicloran were extracted from basic aqueous samples (donor phase, DP) into the microliter volume of organic membrane phase impregnated into the pores of the polypropylene hollow fiber wall, then back extracted into the acidified aqueous solution (acceptor phase, AP) filling in the lumen of the hollow fiber. The mass transfer of the analytes from the donor phase through the organic membrane phase into acceptor phase was driven by both the counter-coupled transport of hydrogen ions and the pH gradient. Afterwards, the hollow fiber was eluted with 50 microL methanol to capture the analytes from both the organic membrane and the acceptor phase. Factors relevant to the enrichment factors (EFs) were investigated. Under the optimized condition (DP: 100 mL of 0.1 M NaOH with 2 M Na2SO4; organic phase: di-n-hexyl with 8% trioctylphosphine oxide (TOPO); AP: 10 microL of 8 M HCl; extraction time of 80 min), the obtained EFs were 405-2000, dynamic linear ranges were 5-200 microg/L (R>0.9976), and limits of detection were 0.5-1.5 microg/L. The presence of humic acid (0-25 mg/L dissolved organic carbon) had no significant effect on the extraction efficiency. The proposed procedure worked very well for real environmental water samples with microgram per liter level of analytes, and good spike recoveries (80-103%) were obtained.
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