A novel electroanalytical approach is used to get insight into scavenger kinetics and mechanism of methylglyoxal (MG) by biguanides metformin, phenformin and 1-phenylbiguanide under the physiological conditions (pH 7.41 and 37 degrees C). The approach is based on monitoring the time profiles of concentrations of the protonated biguanides by ion transfer voltammetry (ITV) at the polarizable room-temperature ionic liquid membrane. Effects of the reactant's concentrations and pH lead us to propose a mechanism including an acid-base reaction of biguanide, which separates the parallel reactions of the protonated and deprotonated biguanide with methylglyoxal. Reaction rate increases considerably in the sequence metformin < phenformin < 1-phenylbiguanide. Kinetic data confirm the previous finding that scavenging of methylglyoxal by metformin is a relatively slow process. Optimization of the background electrolyte enables to use capillary electrophoresis (CE) to detect simultaneously the protonated biguanide and the MG anion in the reaction mixture. CE analysis then yields the mole-to-mole ratios of the reacted biguanides to MG in the range 0.6-0.7 pointing to the simultaneous formation of a 1:1 and a 1:2 reaction products. Usefulness of ion voltammetry or amperometry for further kinetic studies of biguanides, as well as for their assays, can be envisaged. (C) 2016 Elsevier B.V. All rights reserved.