An analytical study of formulations containing malathion

Abstract A total of sixty‐five samples of eighteen different commercial formulations containing malathion were examined in this study. Twelve formulations were found to have a malathion content which was in general agreement with that declared. However, one of these twelve formulations (an emulsifiable concentrate) contained a high level of isomalathion. Five formulations (all emulsifiable concentrates) had significantly lower malathion contents than those declared and were contaminated with malathion analogues, present at concentrations ranging from c.2 to over 100 % mass/mass of the malathion found. These analogues of malathion appear to have resulted from the transesterification of malathion with alcohols used as formulating agents. One formulation (a dustable powder) was found to contain no malathion above the detection limit. Many of the formulations failed tests of their physical properties.