Chromatomass-spectrometric identification of electrochemical transformation products of kresoxim-methyl in solutions

Abstract

The products of electrochemical transformations of organic compounds are similar in many aspects to the products of their chemical reactions. The information on the nature and the formation mechanisms of such products is important for pesticides because this allows characterizing the mechanisms of their decomposition in the soil, aquatic environments and plants. A set of electrochemical processes involving such pesticide of the strobilurin class as kresoxim-methyl [methyl ( E )-2- methoxyimino-2-(2-( o -tolyloxymethyl)­phenyl)acetate] in its solution in aqueous organic medium [mixture of an aqueous solution of ammonium formate (pH 7.4) and acetonitrile (3: 1 v/v)] with the concentration of 100 mg/mL, and the results of chromatomass-spectrometric identification (HPLC-ESI-MS-MS) of the formed products were considered. It has been revealed that hydrolysis products predominate in the mixture of the kresoxim-methyl electrolysis products, including corresponding carboxylic acid and such demethylation products as oximes. Kresoxim-methyl oxidation products, such as the corresponding hydroxamic acid, have been detected in small amounts only. At the same time, the reduction products – amines, most likely formed from oximes, – have been identified. Keeping in mind the restricted information content of the HPLC-ESI-MS-MS method for establishing the structure of the previously uncharacterized analytes, the method of comparing the relative intensities of the peaks of reaction mixture constituents detected in the positive and negative ionization modes was used in identification of the products of electrochemical transformations. The signals of the protonated amines predominate in the first case, while in the second case the compounds containing carboxyl groups ionized at pH 7.4 are detected. Keywords: Pesticides, kresoxim-methyl, electrochemical processes, hydrolysis, oxidation and reduction, identification of products DOI: http://dx.doi.org/10.15826/analitika.2018.22.3.009 (Russian) Tatiana I. Pushkareva, Sergey S. Ermakov, Igor G. Zenkevich, St. Petersburg State University, Universitetskii prosp., 26, St. Petersburg, 198504, Russian Federation