PVC Membrane Electrode for Trinitrobenzenesulfonate and its Use for Indirect Determination of Amino Acids

摘要

A PVC membrane electrode of the conventional type was prepared which is selective for trinitrobenzenesulfonate (TNBS"). It showed a rapid Ner-nstian response within the TNBS" concentration range 1.0 x 1CT5 to 1.0 x 10-2M at 25±O.1°C. The electrode was selective, precise (RSD<0.87% for TNBS" and < 1.32% for amino acids) and usable within the pH range 2.5-12. The standard electrode potentials, E°, were determined at different temperatures and used to calculate the isothermal temperature coefficient of the cell. Selectivity coefficients for numerous compounds are given. The electrode has been used for the direct determination of trinitrobenzenesulfonic acid in aqueous solutions either by the standard additions method or by potentiometric titration against cetyltrimethylammonium bromide (CTABr) at pH 7. The electrode has been also applied successfully for the indirect microdetermination of neutral, acidic and basic amino acids separately, and as binary or ternary mixtures of neutral amino-acids. Total amino acids were determined in urine samples.