A number of organophosphate crop protectors are used to control pests on food crops, but the residues of such crop protectors are potentially harmful. These compounds are inhibitors of the enzyme acetylcholinesterase, and persistent exposure can have adverse effects on health. The organophosphate crop protection ethion (strictly speaking an organothiophosphate, but with the same mode of action, since the P=S bonds are metabolised to P=O bonds) is used on a wide variety of food crops so effective determination of its residue levels is required.
A team of researchers from the Sher-e-Kashmir University of Agricultural Sciences (Srinagar, India) used GC with electron capture detection (ECD) to measure the residue levels of ethion on cucumbers treated with the crop protection. ECD is often thought of as a technique only suitable for halogenated compounds, but it gives strong signals for organophosphates or thiophosphates (such as ethion). Sample preparation was carried out using a modified version of the QuEChERS (quick, easy, cheap, effective, rugged and safe) method, which involves speedy extraction into acetonitrile and fast ‘clean-up’ of the samples prior to injection.