Pest management science

Direct determination of methyl parathion insecticide in rice samples by headspace solid-phase microextraction-gas chromatography-mass spectrometry.

PMID 25472732


The organophosphorus insecticides, especially those based on methyl parathion as active principle, have been used extensively in the protection of rice in Maranhão State, in the north-east of Brazil. This paper describes the optimisation of a solid-phase microextraction (SPME) procedure in confined atmosphere (headspace, HS) for the determination of methyl parathion in rice organic samples by gas chromatography with mass spectrometry detection (GC/MS). The proposed HS-SPME-GC/MS method has been shown to be appropriate for direct analysis of the insecticide in polished rice, with satisfactory results for the following parameters: linearity (correlation coefficient 0.9985), sensitivity (LOD and LOQ of 0.026 and 0.078 µg kg(-1) respectively), precision (coefficients of variation between 6.1 and 22.4%) and accuracy (recoveries varying from 73.2 to 90.0%). Although the efficiency of the proposed GC/MS does not differ statistically (P < 0.05) from the conventional GC/NPD method, given its low cost, speed and also the fact that a minimum volume of toxic effluent is generated, this method can be considered an on-line procedure based on green chemistry. Thus, the analytical methodology satisfies the minimum requirements for control of residues of such insecticides in rice samples destined for human consumption.