Abstract
Conventional determination methods of carbonyl groups in starches are criticized from the practical point of view. The necessity of new methods and the applicability of polarographic methods are discussed. Inapplicability of polarographic method as a direct method of determination for even glucose, monomer of starch and related carbohydrates, is presented and the possibility of indirect methods converting the carbohydrate to electroactive epecies is emphasized.Indirect methods of determination of carbonyl compounds are reviewed and related to the present determination methods based on the formation of quinoxalines from the reaction of the carbohydrate with o-phenylenediamine (OPD).General polarographic behavior of quinoxalines is reviewed.The polarographic OPD method is presented in detail : condition for the reaction of the carbohydrate with OPD, the formation of 2-methylquinoxaline from the reducing end of all the a-l, 4 glucosides and the extraction of the quinoxaline with nhexane or petrolium ether, the linearity of the total limiting current with the reciprocal polymerization degree under fixed conditions. etc.Application of the methods to the determination of number-average molecular weight of amylose, amylopectin and other related carbohydrates are described and compared with those obtained by other methods.The method is also applicable to the determination of carbonyl groups in periodate oxidized starches.
