The Use of Tetramethylbenzidine as an Indicator in the Enzymatic Quantitative Determination of Ethonium

The study considers the possibility of using 3,3',5,5'-tetramethylbenzidine (TMB) as an indicator in the enzymatic analysis for the quantitative determination of quaternary ammonium compounds on the example of ethonium. The feasibility of using TMB as an indicator in the kinetic photometric method has been confirmed. Kinetic curves showing the relationship between the optical density and the ethonium concentration have been constructed. The reaction rates of acetylcholinesterase inhibition by ethonium have been estimated using the tangents of the angles of these curves with TMB as an indicator. The degree of enzyme inhibition has been calculated, and a linear relationship between the ethonium concentration and the degree of inhibition has been determined. This method was applied to determine the ethonium content in 0.1% ethonium gel. The relative standard deviation of the method does not exceed 2.5 %. The approach suggested offers a reliable and accurate method for the quantitative analysis of ethonium in dosage forms.