Dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-diode array detection for the determination of N-methyl carbamate pesticides in vegetables.

This paper described a simple, rapid and efficient method for the determination of N-methyl carbamate pesticides in tomato, cucumber, carrot and lettuce samples by dispersive liquid-liquid microextraction coupled with HPLC-diode array detection. Some experimental parameters that influenced the extraction efficiency, such as types and volumes of extraction and disperser solvents, extraction time and salt effect were examined and optimized. Under optimum conditions, the LOD of the method were 0.5-3.0 μg/kg depending on the compounds and the kind of vegetables. The linearities of the method were obtained in the range of 10.0-300 μg/kg for aldicarb, MTMC, carbofuran and carbaryl, and 20.0-600 μg/kg for isoprocarb, with the correlation coefficients ranging from 0.9921 to 0.9993. The RSD varied from 2.9 to 7.5% (n=5). The recoveries of the method for the five carbamates from vegetable samples at two different spiking levels were ranged from 77.8 to 98.2%. Results showed that the method we proposed can meet the requirements for the determination of N-methyl carbamate in vegetable samples and was finally applied to the analysis of target pesticides in vegetable samples taken from local markets.