Combination of modified ultrasound-assisted extraction with continuous sample drop flow microextraction for determination of pesticides in vegetables and fruits

摘要

A simple, precise and sensitive analytical method, which is a combination of modified ultrasound-assisted extraction (UAE), continuous sample drop flow microextraction (CSDF-ME) and GC-MS, was developed for the extraction and determination of organophosphorus pesticides in fruit and vegetable samples. In this study, for the first time, a very small amount of organic solvent was used for the UAE, almost three times less than conventional UAE. To this end, first, the raw vegetables and fruits were finely chopped and mashed. Then, 0.8 mL of acetonitrile was added and the entire mixture was sonicated for 20 min. Afterward, in order to remove acetonitrile from the mixture and to reduce the amount of organic solvent 6.0 mL of ultra-pure water was added to the mixture, and the aqueous phase was filtered out. Next, the extracted analytes were concentrated by pumping the aqueous phase across a few microliters of organic solvent (chloroform) placed inside the bottom of a conical vial at a flow rate of 0.45 mL min(-1). Finally, the extracted analytes were transferred into the GC-MS for further detection. Under the optimum conditions, the relative recovery ranged from 83.0% to 108.0%. The repeatability of the method was examined at two concentration levels (60.0 and 120.0 ng g(-1)), and it was obtained between 4.0 and 7.6%, and 3.2 and 6.2%, respectively (n = 5). Finally, the LOD and LOQ were found to be 0.2-20.0 ng g(-1) , and 1.0-60.0 ng g(-1), respectively.