| Liquid-phase microextraction(LPME) integrates extraction, separation, purification and concentration. It improves the deficiency of traditional sample preparation methods successfully with its traits, such as easy operation, green protection and high extraction efficiency. With the continuous development of technology, LPME is derived different types and operating mode of microextraction gradually according to different samples and analytes. It has a great development potential and is widely used in environmental, drugs and biological sample analysis, food analysis, clinical medicine and other fields now.This article uses the hollow fiber liquid phase microextraction(HF-LPME) to extract and enrich maleic acid and fumaric acid in complex samples like starch effectively, and then detects their content by high performance liquid chromatography(HPLC). The main research content are as following:1. A novel method for the determination of maleic acid in starch is established by using HF-LPME. By optimizing the control parameters, such as the extraction agent, the p H value of sample solution, temperature, time, stirring rate and salt effect, the optimum conditions are determined. And then extract and analysis under the optimum conditions. The results show that: maleic acid has good linear relation within 0.1-10.0 mg/L, the correlation coefficient is greater than 0.999, the relative standard deviation is 1.7%(n=11), the detection limits of maleic acid is 5.12 μg/L and the enrichment factor can achieve 12.9 times. Through the further research of enrichment factor for LPME, the relationship between enrichment ratio and the initial concentration of maleic acid is found. When the method above is applied to the determination research of maleic acidin a variety of starch samples, the recovery and precision can satisfy the requirements for analysis method, which realize the sensitive and accurate detection of maleic acid in starch samples.2. A novel method for the determination of fumaric acid in caoshanhu hanpian, soil and water is established by using HF-LPME. By optimizing the control parameters, such as the extraction agent, the p H value of sample solution, temperature, time, stirring rate and salt effect, the optimum conditions are determined. And then extract and analysis under the optimum conditions. The results show that: fumaric acid has good linear relation within 0.01-1.0 mg/L, the correlation coefficient is greater than 0.999, the relative standard deviation is 4.3%(n=11), the detection limits of maleic acid is 1.28 μg/L and the enrichment factor can achieve 46.2 times. Through the further research of enrichment factor for LPME, the relationship between enrichment ratio and the initial concentration of fumaric acid is found. When the method above is applied to the determination research of fumaric acid in various samples, the recovery and precision can satisfy the requirements for analysis method, which realize the sensitive and accurate detection of fumaric acid in actual samples.3. A novel method for the determination of maleic acid and fumaric acid at the same time in starch is established by using HF-LPME. Considering the microextraction conditions of two analytes, the optimum conditions are determined finally. And then extract and analysis under the optimum conditions. The results show that: this method can analysis two kinds of components that have similar nature at the same time. When the method above is applied to the determination research of maleic acid and fumaric acid in various starch samples, the recovery and precision can satisfy the requirements for analysis method. By the effect of concentration, extraction and purification of LPME, the sensitivity and selectivity is improved which realize the sensitive and accurate detection for two substances in actual samples and provide a new method for simultaneous determination of various similar components in other complex samples. |
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