Diazomethane Methylation of a Mixture of Chlorophenoxy Acids and Dinitrophenols

Abstract

Three different methylation procedures using diazomethane were evaluated on 2,4-D, 2,4,5-T, 2,4,5-TP, 2,4-DB, 2,3,6-TBA, DNOC, DNBP, and DNOCHP: (I) diazomethane alone, (II) diazomethane and methanol, (III) diazomethane, methanol, and HC1. Evaluations were made by comparing electron capture GLC peak heights or peak areas of reacted products with those of standards. Volatility losses were observed with method I. Completeness of dinitrophenol methylation varied with the lot of methanol used with methods II and III. From the results of this study, method I was modified by the addition of isooctane to the reaction vessel to prevent the sample from evaporating to dryness and the use of a 70°C water bath to speed up the reaction. Conversion of all pesticides by the modified procedure was over 90%.

Pesticide Residues

“…Howard and Yip (174) reported on the diazomethane methylation of a mixture of chlorophenoxy acids and dinitrophenols. In an improved procedure, isooctane was added to the reaction flask to prevent the sample from evaporating to dryness and a 70 °C water bath was used to speed up the reaction.…”