Distribution of pesticide residues in rice grain and in its coproducts

Abstract

Pesticides are used to prevent pests from attacking grains in order to preserve the crops. This paper aims at evaluating the distribution of the pesticides bispyribac-sodium, carbofuran, clomazone and tebuconazole in different fractions of milled rice (white rice, rice bran, husked rice, parboiled rice, parboiled rice bran, and husked parboiled rice) which is planted on experimental felds under controlled conditions. The QuEChERS method was adapted to the extraction of pesticides and validated by using HPLC-DAD for quantifcation and LC-MS for confrmation. The analytical method of extracting pesticides, as well as the chromatographic conditions for identifcation and quantifcation, were suitable, according to certain effciency indicators: 0.07 mg kg-1 LOD and 0.2 mg kg-1 LOQ for the mixture of pesticides and rice and rice bran recoveries of 119 and 116%, 84 and 119%, 113 and 96%, 103 and 97% for carbofuran, bispyribac-sodium, clomazone and tebuconazole, respectively. The method under development was applied to rice fractions: bran had the highest residue concentration of the studied pesticides, when compared to milled rice, showing 8.0, 2.3, 2.2 and 1.6 times more contamination, in average, with tebuconazole, clomazone, carbofuran and bispyribac-sodium, respectively. Only clomazone and tebuconazole were in the acceptable limits established by Codex Alimentarius (0.1 mg kg-1) for milled rice. © 2011 Sociedade Brasileira de Química.