Simultaneous Determination of Residual Amounts of 37 Pesticides in Rice by Gas Chromatography

Thirty-seven pesticides in rice were determined simultaneously by GC with PFPD and ECD after separation by dispersive-solid phase extraction (DSPE).Sample of rice was extracted homogeneously with mixture of acetone-hexane(25+75) as dispersion agent.The extract obtained was purified by DSPE through shaking with mixture of C18,ethylene diamine-N-propylsilane (PSA) and anhydrous magnesium sulfate in the sample flask.The supernatant was used for GC analysis with PFPD and ECD.Linearity ranges of 13 organochlorine,16 organophosphorous and 8 pyrethroid pesticides were kept in the ranges of 0.02-0.2 mg·L-1,0.1-1.0 mg·L-1 and 0.1-1.0 mg·L-1 respectively.Detection limits (3S/N) found were less than 0.02 mg·kg-1.Tests for recovery and precision were made by addition of standard solutions of the 37 pesticides at 3 different concentration levels to rice sample which was then analyzed by the proposed method.Values of recovery obtained were in the range of 71.8%-111.8% and values of RSD′s (n=3) were in the range of 1.1%-14.0%.