MODIFIED COLORIMETRIC METHOD FOR THE DETERMINATION OF MALATHION

A thorough investigation has been made of the recommended method for the determination of malathion, and the major cause of two of the most serious problems in this method has been resolved. The method that uses a copper(II) complex as the basis of colorimetric measurements suffers from the disadvantage that the colour fades quickly and that an increase of a few seconds in the contact time of the copper(II) solution and the hydrolysis product of malathion results in a reduction in the intensity of the yellow colour. Attempts to overcome these drawbacks have been reported, some of which are tedious and others only partially successful, but it is suggested that if copper is replaced with bismuth the problems may be more simply resolved. Isomalathion does not react in this method.