| In the past few years, a simple and virtually solvent free method known as liquid-phase microextraction (LPME) has emerged dramatically as an alternative sample preparation technique. This novel technique overcomes a few disadvantages of conventional Sample preparation techniques, such as time-consuming, labor-intensive and requiring large amounts of toxic organic solvents which may result in secondary environmental pollution. The LPME combines extraction, concentration and sample introduction in a single step and is a simple, cheap, sensitive and environmental friendly sample preparation technique. Especially in the the hollow fiber LPME, since organic-phase is protected by the hollow fiber, the stability of the solvent"drop"is greatly improved, and higher stirring rates can be used to reduce the equilibrium time and extraction time. As a result, better extraction efficiency and sensitivity are achieved. Moreover, the hollow fiber can also prevent from the interferences caused by large molecules or suspended solid particles in sample solutions. At present, the LPME technique has been widely applied in various fields, such as organic pollutants in environment analysis, biology, detection of food, etc. However, there are very few relevant reports about the application of LPME in our country. This paper studies the followings:1. The application of dynamic hollow fiber liquid-phase microextraction (dynamic HF-LPME) combined with gas chromatography-mass spectrometry (GC-MS) for the determination of trace amounts of polychlorinated-biphenyls (PCBs) in water was studied. The extraction efficiencies in three different liquid-phase microextraction (LPME) modes (static direct-immersed LPME, static HF-LPME and dynamic HF-LPME) were investigated and dynamic HF-LPME was finally selected for present purpose. The experimental parameters that affect the extraction efficiency of dynamic HF-LPME, such as organic solvent selection, solvent volume, extraction time, dwelling time, extraction temperature, stirring rate and salt content were optimized.Under the optimum conditions, the concentration enrichment factors for PCBs were from 718-fold to 840-fold. The calibration curves were linear over a range of 0.05–90μg/L, with a correlation coefficient (r2) of 0.9957–0.9979. The relative standard deviation (R.S.D.) ranged from 3.4% to 5.8% for intra-day variation and from 4.1% to 7.3% for inter-day variation. The limits of detection (LODs, S/N=3:1) were calculated in a range of 13–41 ng/L. The recoveries for spiked water samples ranged from 85.9% to 92.0%.2. Application of hollow fiber membrane/liquid-phase microextraction combined with gas chromatography-mass spectrometry on the determination of three fungicides (chlorothalonil, metalaxyl, triadimefon) in water was studied. The variable experimental conditions for the HF-LPME extraction process were optimized. The ideal experimental conditions were as follows: 3μL of toluene as the extraction solvent; 10 ml aqueous sample without NaCl addition was extracted for 15 min; extraction temperature of 45°C; 500 r/min of stirring speed. After extraction, 1.0μL of the organic solvent was then injected into GC–MS for further analysis. Under these conditions, the concentration factors for the three fungicides were 140–450. The calibration curve was linear over a range of 5–1000μg/L. The detection limits(S/N=3) were 0.5–1.3μg/L, The recoveries for real water samples were in range of 92.3%–96.0%. Results indicated possibility of applying HF-LPME in analysis of the three fungicides in water attributed to of the convenience, sensitivity low cost of the method.
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