| Liquid phase microextraction (LPME) is a new sample pretreatment technique that integrates sampling, extraction and concentration into a single step and only little organic solvent is required. In overseas, Liquid phase microextraction (LPME) combined with gas chromatography (GC) or gas chromatography-mass spectrum (GC-MS), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) is primarily applied for the analysis of non-volatile and fixed environmental contaminations and drugs of low concentration in biological samples but comprehensive application in our country is uncreated.1. The recent progress of several sample pretreatment methods are reviewed.2. A rapid method for the determination of lidocaine in urine by liquid-phase microextraction (LPME) coupled with high performance liquid chromatography (HPLC) was developed. Extraction solvent, extraction time, solvent volume, and pH were optimized. The linear range was from 0.2 mg/L to 5 mg/L, the detection limit was 0.1 mg/L, and the relative standard deviation was lower than 6.3%. With LPME, some substances in urine which interfered the determination of lidocaine were eliminated efficiently, and the higher selectivity was obtained. The method with little solvent consumption was simple, fast, sensitive and suitable for the determination of lidocaine in urine.3. A simple liquid-phase microextraction (LPME) device combined with high-performance liquid chromatography (HPLC) is presented forthe simultaneous analysis of local anaesthetics, lidocaine, bupivacaine, and tetracaine, from human urine sample. An organic solvent showed good compatibility with the mobile phase of the HPLC, o-dibutyl phthalate, was selected. Local anaesthetics are extracted from 6-mL of the feed aqueous solution and human urine sample into a water-immiscible organic solvent suspended at the needle tip of the microsyringe, then the organic solvent was directly introduced to a re versed-phase HPLC system. The kind of the organic extraction solvent, the stirring rate, the pH value of the aqueous feed solution and the extraction time have been discussed. At the optimized extraction conditions, a high enrichment factor (more than 86.0-fold) and significant sample clean-up for all of studied local anaesthetics were achieved within 30 min. The detection limits (lower than 0.05 ug/mL) were comparable with previously reported gas chromatography methods. This method was applied to specimen of patient who was treated with extradural anaesthesia of lidocaine, bupivacaine, and tetracaine, and revealed that simultaneous determination of above three local anaesthetics in human urine was possible.4. Liquid-liquid-liquid microextraction (LLLME) coupled with high-performance liquid chromatography (HPLC) was developed for the simultaneous determination of four kinds of local anaesthetics in human urine. The effect of extraction solvent, the volume of organic solvent, stirring rate, extraction time, pH in the donor phase, HCl concentration in the acceptor phase, and salt addition in the donor phase on the enrichment factor of analytes were investigated. At the optimized extraction conditions, high enrichment factors (more than 800-fold) were obtained within 50 min. Significant clean-up and high selectivity were obtained.
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