Fang Han

University of Science and Technology of China, Luchow, Anhui Sheng, China

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Publications (8)21.32 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: An analytical technique of in-line coupling headspace liquid-phase microextraction (HS-LPME) with capillary electrophoresis (CE) was proposed to determine volatile analytes. A special cover unit of the sample vial was adopted in the coupling method. To evaluate the proposed method, phenols were used as model analytes. The parameters affecting the extraction efficiency were investigated, including the configuration of acceptor phase, kind and concentration of acceptor solution, extraction temperature and time, salt-out effect, sample volume, etc. The optimal enrichment factors of HS-LPME were obtained with the sample volume of about half of sample vials, which were confirmed by both the theoretical prediction and experimental results. The enrichment factors were obtained from 520 to 1270. The limits of detection (LODs, S/N=3) were in the range from 0.5 to 1 ng/mL each phenol. The recoveries were from 87.2% to 92.7% and the relative standard deviations (RSDs) were lower than 5.7% (n=6). The proposed method was successfully applied to the quantitative analysis of the phenols in tap water, and proved to be a simple, convenient and reliable sample preconcentration and determination method for volatile analytes in water samples.
    No preview · Article · Feb 2010 · Journal of Chromatography A
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    ABSTRACT: A simple and efficient dual preconcentration method of on-column liquid-liquid-liquid microextraction (LLLME) coupled with base stacking was developed for capillary zone electrophoresis (CZE) in this paper. Four N-methyl carbamates were used as target compounds to evaluate the enrichment means. The carbamates in sample solutions (donor phase) were extracted into a dodecanol phase immobilized on a porous hollow fiber, hydrolyzed and back extracted into 0.20 microL running buffer (acceptor phase) of 30 mmol/L methylamine hydrochloride (pH 11.6) containing 0.5 mmol/L tetradecyltrimethylammonium bromide inside the hollow fiber, stacked further with 0.5 mol/L NaOH injected at -10 kV for 60s, and separated by CZE. Analytical parameters affecting the LLLME, base stacking and CZE were investigated, including sample solution volume, pH and temperature, extraction time, stirring rate, buffer component, buffer pH, NaOH concentration, stacking time, etc. The enrichment factors of the carbamates were higher than 1100. The relative standard deviation (RSD) of peak height and limits of detection (LODs) were 4.5-5.5% (n=6) and 2-4 ng/mL (S/N=3) for standard solutions, respectively. The proposed method was applied to the analysis of vegetable and fruit samples with the RSD less than 6.0% (n=3) and LODs of 6-10 ng/g (S/N=3). The calibration solutions were prepared by diluting the stock solutions with blank sample solutions, and the calibration concentrations ranged from 0.012 to 1.0 microg/mL (r>0.9951). The analytical results demonstrated that the LLLME coupled with base stacking was a simple, convenient and reliable on-column sample pretreatment method for the analysis of anionic analytes in CZE.
    No preview · Article · Apr 2009 · Journal of Chromatography A
  • C.-Z. Yu · Y.-Z. He · L. Li · F. Han · W.-E. Gan
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    ABSTRACT: A selective and sensitive method for the determination of kanamycins with post-column derealization in capillary zone electrophoresis and laser induced fluorescence detection was proposed. The derivatization reaction was carried out using a coaxial-gap reactor with a derivatization reagent of naphthalene-2, 3-dicarboxaldehyde (NDA). The labeled kanamycins were detected with the excitation wavelength at 473 nm in laser induced fluorescence. The separation was carried out at - 15 kV with reversed electroosmotic flow in 50 mmol/L sodium acetic buffer (pH 5.0) containing 0. 5 mmol/L cetyltrimethyl ammonium. The derivatization was performed with the derivatization reagent of 1.0 mmol/L thalene-2, 3-dicarboxaldehyde, 8.0 mmol/L 2-merc-aptoethanol and 35 mmol/L soldium (pH 10.0) in 30% (V/V) methanol tetraborate buffer. The limits of detection for kanamycins ranging from 3.6 × l0 -5 to 5.2 × 10 -5 g/L and the separation efficiencies from 2.0 × 10 5 to 2.4 × 10 5 theoretical plates were obtained. The method has been employed to analyze kanamycin residues in animal tissues.
    No preview · Article · Nov 2008 · CHINESE JOURNAL OF ANALYTICAL CHEMISTRY
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    ABSTRACT: An electrokinetic flow analysis system (EFA), consisting of one electroosmotic pump, five solenoid valves and one on-line homemade solid phase extraction (SPE) unit, combined with capillary zone electrophoresis (CZE) was proposed to determine benzoic acid and sorbic acid in food products. Tetrabutylammonium bromide (TBAB) was adopted as an ion pair reagent to improve the retention of the preservatives on C(8)-bonded silica sorbent, which was also used to remove sample matrices. By using the SPE unit, the EFA-SPE-CZE system was able to perform the SPE operation and CZE separation simultaneously. With a modified interface of EFA and CZE, the buffer consumption was reduced to 130 microL for each running. The preservatives were separated and determined under optimized conditions with p-hydroxybenzoic acid as an internal standard. The relative standard deviation (R.S.D.) of peak area for each analyte was less than 3.1% (n=5) and the limits of detection (LODs) ranged from 10 to 20 ngmL(-1) (K=3, n=11).
    Full-text · Article · Jul 2008 · Analytica chimica acta
  • Fang Han · You-Zhao He · Chang-Zhu Yu
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    ABSTRACT: A convenient and automated method for on-line pretreatment and determination of three parabens (i.e. methyl, ethyl and propyl p-hydroxybenzoate) in cosmetic products is proposed by using flow injection analysis (FIA), solid-phase extraction (SPE) and micellar electrokinetic chromatography (MEKC). An improved split-flow interface is used to couple SPE on C(8)-bonded silica with MEKC separation, which can avoid running buffer contamination and reduce buffer consumption, especially, containing expensive reagents. The analytes are loaded onto a C(8) column at 0.6 mL/min for 60s and eluted with a mixed eluent of 40% (v/v) 10 mmol/L sodium tetraborate buffer (pH 9.3) and 60% (v/v) ethanol at 0.75 mL/min. The MEKC separation is accomplished with a running buffer of 20 mmol/L sodium tetraborate (pH 9.3) containing 100 mmol/L sodium dodecyl sulfate (SDS) at 15 kV. For butyl p-hydroxybenzoate did not be detected in the cosmetic products, it was used as an internal standard (IS) added into the real samples. This FIA-SPE-MEKC method using IS allows the sample separation within 12 min and the sample throughput of five samples per hour with the relative standard deviation (R.S.D.) less than 2.3% (n=5). The limits of detection (LOD) are in the range from 0.07 to 0.1 microg/mL (S/N=3 and n=11). The proposed method has been used to determine three parabens in real cosmetic products satisfactorily.
    No preview · Article · Mar 2008 · Talanta
  • F. Han · Y.-Z. He · G.-N. Fu · H.-Y. Xie · L. Li · W.-E. Gan
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    ABSTRACT: A combined system of electrokinetic flow analysis (EFA) and micellar electrokinetic capillary chromatography (MEKC) was proposed to determine six preservatives in food samples. The EFA system consists of one homemade electroosmotic pump, five solenoid valves and one solid-phase extraction (SPE) microcolumn. The electroosmotic pump and solenoid valves were controlled by a personal computer with a homemade interface card and a Visual C program written by our group. An interface of EFA and MEKC was designed to reduce running buffer consumption, espexcially for the buffer solution containing expensive reagent. The running buffer of MEKC was 20 mmol/L disodium tetraborate (pH 9.3) containing 100 mmol/L SDS. p-hydroxybenzoic acid(PBA) was adopted as an internal standard. The proposed method can separate and determine the preservatives within 15 min, with the relative standard deviation of peak area less than 3.4% (n = 5), limits of detection ranged from 0.04 to 0.1 mg/L(S/N = 3, n = 11) and recoveries ranged from 91.4% to 104%. The EFA system was simple, convenient and easy to be controlled automatically.
    No preview · Article · Jan 2008
  • G.-N. Fu · Y.-Z. He · F. Han · W.-E. Gan
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    ABSTRACT: An electrokinetic flow analysis (EFA) system was developed for the determination of phenolic compounds in water samples. The analyte preconcentration and matrix clean-up was performed by an on-line liquid-liquid-liquid microextraction (LLLME) unit. The EFA system consisted of one homemade electroosmotic pump and four solenoid valves, which were controlled by a personal computer with a homemade interface card and Visual C program. The obtained conditions were as follows : dodecanol was used as the orginic solvent of liquid membrane supported by a 10 cm ×450 μm i. d. polypropylene hollow fiber, 10 μL 0.25 mol/L NaOH was the back-extracting solution, a sample flow rate of 2.0 mL/min and 7.5 times through the extraction channel back and forth were chosen in the analysis. When the total phenolic compounds in 1 mL wastewater was determined, the analytical time needed 9 min, the enrichment factor and limit of detection ( LOD) were 53 and 3 μg/L respectively, which were much lower than the maximum allowed level in industrial wastewater. The linear concentration ranged from 9. 4 × 10-3 to 5.7 mg/L phenol, which were adopted as a converted concentration for total phenols. When the total phenolic compounds in 6 mL surface water was determined, the analytical time was 49 min, the enrichment factor and LOD were 300 and 0.6 μg/L respectively, which were lower than the maximum allowed level in surface water. The linear concentration ranged from 1.7 ×10-3 to 1.0 mg/L phenol.
    No preview · Article · Jan 2008
  • Chang-Zhu Yu · You-Zhao He · Fang Han · Guo-Ni Fu
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    ABSTRACT: A post-column reactor with coaxial-gap mode is developed for laser-induced fluorescence detection (LIF) in capillary electrophoresis (CE). The reactor can be assembled simply and conveniently, in which a thin polyimide sleeve of 10-mm length obtained from the capillary coating is used to align separation and reaction capillary with a 20 microm gap. Naphthalene-2,3-dicarboxaldehyde and 2-mercaptoethanol are used as derivatization reagents and delivered into the reaction capillary through the annulus between the separation capillary and polyimide sleeve and the gap of two capillaries by gravity. A reaction distance from the gap to detection point is 5mm. For the post-column reactor of CE-LIF, several configuration parameters are optimized, including liquid level difference between the derivatization solution and outlet buffer, annular dimension between the outer diameter of etched separation capillary and the inner diameter of polyimide sleeve, and reaction distance, etc. The detection limits in the range from 8.0x10(-8) to 1.0x10(-6) mol/L and linear calibration range more than two orders of magnitude are obtained for amino acids. The separation efficiency ranges from 1.35x10(5) to 1.67x10(5) theoretical plates.
    No preview · Article · Dec 2007 · Journal of Chromatography A