| Sample pretreatment technology refers to the sample preparation and sample decomposition and dissolution using appropriate methods and the process of treatment of test components through extracted, purified and concentrated, so that the determined analytes can be transformed into the form to be quantitative and qualitative analysis and detection. Sample pretreatment is designed to eliminate the matrix interference, improve accuracy, precision, selectivity and sensitivity of the method. Therefore, sample pretreatment is the key to the process of analysis and detection. If you choose the improper pretreatment methods, it may often lead to loss of certain components, the impact of disturbance component can not be completely removed or introduced new impurities. But as long as the detection instruments are stable and reliable, reproducibility and accuracy of test results mainly depends on the sample preparation. Sensitivity of a new kinds of detection method and its analysis speed also have an important relationship with the sample pretreatment process and the complexity of sample pretreatment.High performance liquid chromatography (HPLC) method is the most commonly used chromatographic method for qualitative and quantitative analysis of substances. Compared with the classical liquid chromatography, HPLC has the characteristics with high analysis speed, high separation efficiency, high selectivity, high sensitivity and operation of automation and so on. Therefore, high performance liquid chromatography is widely used in the fields of medicine, biochemistry, natural products, environmental analysis, agricultural analysis and food safety inspection.In this paper, several fast and efficient sample pretreatment techniques such as solid phase extraction, cloud point extraction and ionic liquid dispersive liquid-phase microextraction are used for purification ofβ-agonists in feed and erythrosine in beverages, combined with HPLC for separation and detection.The main contents are as follows:1. Simultaneous determination of cimaterol, salbutamol, terbutaline, and ractopamine in feed by solid phase extraction coupled to ultra performance liquid chromatographyAn ultra performance liquid chromatography (UPLC) method was established for the simultaneous determination of cimaterol, salbutamol, terbutaline, and ractopamine in feed. Target compounds were extracted with methanol and centrifuged. The supernatant was then transferred and concentrated, and applied to a solid phase extraction MCX cartridge for clean-up before UPLC analysis. The calibration curves for the four beta-agonists were good linear in concentration range of 0.05-1μg mL-'with the correlation coefficients (r) over 0.999. The average recoveries were in the range of 90.1 to 101.4% with relative standard deviation values lower than 8.0%.2. Simultaneous determination of fiveβ-agonists in feed by solid phase extraction coupled to ultra performance liquid chromatographyAn ultra performance liquid chromatography (UPLC) method was established for the simultaneous determination of dopamine, cimaterol, salbutamol, terbutaline, and ractopamine in feed. Target compounds were extracted with methanol and centrifuged. Two equal supernatants were taken:one was applied to a solid phase extraction Alumina A cartridge after acidified and the other was applied to a MCX cartridge when it was concentrated and dissolved in 2% acetic acid. The former was eluted with 1 mol L-1 hydrochloric acid-methanol (1/9, v/v) and the later was eluted with 5%(v/v) ammonia hydroxide in methanol. The elutes were combined and then evaporated to dryness under a stream of nitrogen at 40℃and dissolved in 1.0 mL of sodium dihydrogen phosphate (10 mM, pH 2.7) for UPLC analysis after being filtered through a 0.22μm membrane. The calibration curves for the five beta-agonists were good linear in concentration range of 0.05-1μg mL-1 with the correlation coefficients (r) over 0.996. The average recoveries were in the range of 77.9 to 99.7% with relative standard deviation values lower than4.3%.3. Cloud point preconcentration to the determination of erythrosine in soft drinks by high-performance liquid chromatography with UV detectionA new analytical method for the determination of erythrosine in soft drinks was developed using the cloud point extraction of non-ionic surfactant (Triton X-114) prior to high-performance liquid chromatography with ultraviolet detection (HPLC-UV) analysis. The comound was extracted from 10.0 mL of different soft drinks and a preconcentration factor of 50 was obtained. The proposed method showed good linear relationship in the concentration range of 0.002-5μg mL-with the correlation coefficient over 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were 0.5 ng mL-1 and 1.5 ng mL-1, respectively. The average recoveries were in the range from 86.5% to 97.1% with relative standard deviation value lower than 5.7%.4. Determination of erythrosine in soft drinks by ionic liquid dispersive liquid-phase microextraction coupled with high-performance liquid chromatographyA new approach for the determination of erythrosine in soft drinks by ionic liquid based dispersive liquid-phase microextraction (IL-DLME) prior to high-performance liquid chromatography with ultraviolet detection (HPLC-UV) was developed. This technique selects the ionic liquid instead of a volatile organic solvent as the extraction solvent, and combines extraction and concentration of the analyte into one step. 1-Octyl-3-methylimidazolium hexafluorophosphate [C8MIM][PF6] was used as the extraction solvent and the factors affecting the extraction efficiency such as the volume of [C8MIM][PF6], amount of methanol, pH of working solutions, extraction time, and dissoluble temperature were optimized. The proposed method showed good linear relationship in the concentration range of 0.005-5μg mL-1 with the correlation coefficient (r) over 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0 ng mL-1 and 6.0 ng mL-1, respectively. The average recoveries were in the range from 83.6% to 95.6% with relative standard deviation values lower than 8.4%. This method has the advantages of simplicity of operation, rapidity, low cost, high recovery, and enrichment factor. |
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