Determination Of Phoxim And Profenofos Residues In Fruits And Vegetables And The Study Of Their Degradability

Hollow fiber liquid phase microextraction(HF-LPME)technology is a green and environment-friendly sample pretreatment technique which has been developed rapidly in recent years.It has many advantages such as high extraction efficiency,simple operation,good repeatability and easy to combine with various detectors(GC,HPLC,ICP-AES,ICP-MS etc.).It has been widely used in various trace analysis fields,such as chemistry,biology,drug,environment and food.The hollow fiber liquid phase microextraction has been used to extract and enrich phoxim in vegetables and profenofos in citrus fruits,and then their contents have been detected by high performance liquid chromatography.In addition,the degradation of phoxim in vegetable samples has been studied in different storage and cleaning methods.The main research contents are as follows:1.The method for the determination of phoxim in vegetables was established by HF-LPME-HPLC.The optimum relevant parameters affecting the extraction efficiency of phoxim were obtained by choosing the extraction agent,the p H value of sample solution,extraction temperature,stirring rate,extraction time,and salt effect.The experimental results showed that there was a good linear relation within 0.005?1.0 mg·L-1,the correlation coefficient is greater than 0.9990,the relative standard deviation(RSD)was 1.8%.By calculation,when the signal-to-noise ratio(S/N)was 3,the detection limit(LOD)of phoxim was 1.3 ?g·L-1 and the enrichment factor was 325 times.When the above method was applied to the determination of actual vegetable samples,the spiked recovery rates of the samples can reach 84.0?92.0%,and the RSDs were 1.9?4.2%,which realizes the rapid,sensitive and accurate determination of phoxim in vegetable samples.2.The method for the determination of profenofos in citrus fruits was established by HF-LPME-HPLC.The optimum relevant parameters affecting the extraction efficiency of profenofos were obtained by choosing the extraction agent,the p H value of sample solution,extraction temperature,stirring rate,extraction time,and salt effect.The experimental results showed that there was a good linear relation within 0.005?1.0 mg·L-1,the correlation coefficient is greater than 0.9990,the relative standard deviation(RSD)was 1.8%.By calculation,when the signal-to-noise ratio(S/N)was 3,the detection limit(LOD)of profenofos was 1.1 ?g·L-1 and the enrichment factor was 361 times.When the above method is applied to the determination of actual itrus fruitc samples,the spiked recovery rates of the samples can reach 81.8?91.2%,and the RSDs were 1.2?3.1%,which realizes the rapid,sensitive and accurate determination of phoxim in citrus fruit samples.3.The method of HPLC was used to study the degradation of phoxim in vegetable sample in different storage and cleaning methods,and provided some theoretical references and guidance for related food safety determination and daily life of human beings.The results showed that:(1)In the same storage conditions(temperature,time),the degradation of phoxim varied with the type of vegetables,and with storage time or storage temperature increase,the degradation of phoxim in the same vegetable sample was higher.(2)In the other same storage conditions,with the increase of refrigerating time,the degradation of phoxim in tomato sample adding preservatives(such as benzoic acid,sorbic acid and sodium sulfite)were lower than those without preservatives,and the degradation of phoxim in tomato which had added benzoic acic were lower than added sodium nitrite and sorbic acid.(3)Clear water,different types of cleaning agents,and ultrasonic cleaners can reduce the residual amount of phoxim in lettuce and tomato vegetables samples,and in the same cleaning method,the degradation of phoxim varies with the type of vegetables.(4)Flushing with clear water is easier to degrade phoxim in vegetables than with water soaking,and the degradation of phoxim decreased with the immersion time in clear water.(5)In the same treatment time,with the increase of the concentration of chemical detergents(acetic acid,sodium bicarbonate,sodium chloride),the degradation of phoxim in lettuce and tomato samples were higher,and the degradability of phoxim gradually increased with increase of treatment time in the same concentration detergents.(6)It was found that the self-made enzyme green environmental cleaning agent also had a certain effect on the degradation of phoxim in lettuce and tomato.