Water Content Using Karl-Fisher Aquametry and Loss on Drying Determinations Using Thermogravimeter for Pesticide Standard Materials

Abstract

In the Japanese Food Sanitation Law, the water content or loss on drying (LOD) value of standard materials for pesticide residue analysis is not officially designated. In the present study, to investigate the actual situation of the water content or LOD value of commercial pesticide standards, 40 pesticide standards were determined by the Karl-Fisher aquametry (KF) and 24 pesticide standards were done by a thermogravimetric analysis (TGA). Furthermore, the applicability of KF and TGA was also discussed. The water content or LOD values of most pesticides were within 1%, therefore they are regarded as having the negligible values within the limit of error for the residual pesticide analysis. However, since some pesticides, dichloropropionic acid sodium salt, sodium dimethyl dithiocarbamate, paraquat, diquat dibromide, formamidine hydrochloride, maneb, iminoctadine triacetate, mancozeb and monocrotophos, had relatively large amounts of water or LOD values, the water content and LOD value of such pesticides should be carefully considered during the pesticide residue analysis. For comparison of KF and TGA, there are differences in both the data for some pesticide standards. The reason seems that the pesticides interfere with the KF redox reaction.