Studies On Subcritical Water Extraction Pretreatment And Its Applicaton In Food Analysis

Food safety is a hot topic in China currently. The complicated matrix of the sample, the low concentration of the determinants and the variety of the sample are main characteristics of food analysis. In the situation of the monitoring of food safety, rapid analysis is necessary because of the large amount of samples. Sample preparation play a key role in food safety. The research and development of rapid,simple and green pretreatment technologies in food analysis is in the edge-of-state of this field.In this paper, a new food sample preparation technique, subcritical water extraction, has been studied and applied to the extraction of nitrite and carbamate pesticides from meat and vegetables respectively. The optimized conditions of subcritical water extraction have been studies too. The main results of this thesis are as follows:(1) The extraction of nitrite from meat by subcritical water was studied. Factors such as temperature, extraction time and the composition of extraction solvent were investigated. The optimal conditions were obtained to be: 5 ml saturated borax solution, 20ml deionized water under 120℃for about 15 min. Compared with the National Standard Method of People's Republic of China(GB/T 5009.33-2003), the subcritical water extraction method needs less reagent and achieves higher extraction efficiency. This method can be successfully used in the analysis of the practical sample. The solidification of reagent for nitrite was studied too.(2) The extraction of carbamate pesticides by subcritical water extraction technology was also studied. Factors, such as temperature, extraction time, pH and the volume of extraction solvent were investigated. The optimal conditions were obtained to be: 5 ml extraction solution that pH is 8.0 under 120℃for about 5 min. Compared with manual shaking extraction, subcritical water extraction has a higher extraction efficiency, better precision and simpler operation。...