New sorptive extraction method based on polydimethylsiloxane sieve combined with GC-MS for determination of pyrethroid residues in tea

In this study, a polypropylene sieve with porous network structure was coated with polydimethylsiloxane (PDMS) and used as extraction phase. Based on the PDMS-sieve, a rapid, simple and sensitive sorptive extraction method was established for analysis of five pyrethroid residues in tea samples. In the method, pyrethroids in a stirred solution were extracted on a PDMS-sieve, the analytes loaded on the sieve were then ultrasonically desorbed in ethyl acetate and analyzed by gas chromatography-mass spectrometer (GC-MS) with selected ion monitoring mode (SIM). The proposed method was optimized and validated, the matrix-matched calibration curves were performed at six concentration levels and good linear correlations (r) were obtained (r >= 0.9907) within the range of 0.001-0.1 mu g mL(-1). The detection limits (LODs) of five pesticides ranged from 0.8 ng g(-1) to 19.6 ng g(-1). Good repeatability was obtained with the inter- and intra-day relative standard deviation (RSDs) values lower than 10%. The method has been applied successfully to the determination of pyrethroids in six tea samples, and satisfactory recoveries ranging from 82% to 111% were obtained. The results indicated that the proposed method is suitable for trace analysis of pesticides residues in tea samples.