The analysis of crops to determine neutral conjugates of an N-hydroxymethyl derivative of monocrotophos insecticide

Abstract

Following the application to plants of the organophosphorus insecticide monocrotophos (AZODRIN; dimethyl cis-1-methyl-2-methylcarbamoylvinyl phosphate), an N-hydroxymethyl derivative can sometimes be detected as a breakdown product. This product is capable of conjugation with plant sugars, and the present paper describes the development of an analytical method for the determination of this conjugate.

In the laboratory, the conjugate can be converted into a complex mixture of enzyme inhibitors by reaction with hydrochloric acid. However, if the reaction is carried out in the presence of butane-2-thiol, the reaction can be controlled, and there is quantitative conversion into an s-butyl thioether. This derivative can be determined down to a level of 0·03 p.p.m. by a cholinesterase inhibition technique, and added specificity can be obtained by carrying out the inhibition reaction directly on a thin-layer plate after chromatography.

The verification of the procedure by using radioisotope techniques is described.