| A novel mult-function flow analysis system---electrokinetic flow analysis system (EKFA) was developed for simultaneous separation and pre-concentration of heterogeneous ion analytes with extremely low concentrations. The experimental technique and analytical application of EKFA system was discussed and the analytical conditions were optimized. Moreover, an integrative coupling technique of headspace liquid-phase microextraction (HS-LPME) and capillary zone chromatography (CZE) was proposed and applied to the analysis of preservatives in food sample and soft drinks.(1) Determination of caffeic acid and gallic acid in tea samples by capillary electrophoresis with bi-directional electrostackingAn analytical method combining bi-directional electrostacking with capillary electrophoresis was proposed to analyze organic acid ions in tea samples. Salt bridges were replaced by porous cores to separate running buffer and electrode solution, which made the bi-directional electrostacking setup integratively. The analytical procedure was controlled by a computer. The parameters were investigated, including electrostacking time, applied voltage, sample volume, etc. Under the optimal conditions, the enrichment factors of caffeic acid and gallic acid were 24 and 20, respectively. The limits of detection ranged from 0.2 to 0.4μg/mL.(2) Determination of benzoic acid and sorbic acid in food sample and soft drink by integrative headspace liquid-phase microextraction and capillary zone chromatographyAn integrative coupling technique of headspace liquid-phase microextraction (HS-LPME) and capillary zone chromatography (CZE) was proposed and applied to the analysis of benzoic acid and sorbic acid in food and soft drink samples. The analytical technique was performed with one separation capillary to fix the acceptor volume, hold the microextraction droplet, inject the concentrated analytes and separate the analytes by CZE. A running buffer solution droplet was formed at the inlet of the capillary by pressure. The HS-LPME was carried out with 6 mL sample solution containing 0.25 g/mL NaCl in a 14-mL sample viel at 90℃for 30 min. At last, the concentrated analytes were injected at 10 cm height difference for 20 s and separated by CZE. The enrichment factors of benzoic acid and sorbic acid is 404 and 266, respectively. The limits of detection were from 0.01 to 0.03 mg/L, and the recoveries were in the range of 88.7?104.6%. The integrative coupling technique was able to concentrate analytes and eliminate the matrix interference effectively, and be used to determine analytes in complex samples by CE(3) Development of integrative headspace liquid-phase microextraction and capillary chromatographyFor the latest development in the integrative headspace liquid-phase microextraction and capillary electrophoresis in our group. Using an alkaline solution as the extraction phase has been successfully applied to separate and determine the phenol analytes in tap water. There also a significant progress in the detection of the ester preservatives in medicine samples by the integrative headspace liquid-phase microextraction and capillary electrophoresis. |
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