PVC MEMBRANE-ELECTRODE FOR TRINITROBENZENESULFONATE AND ITS USE FOR INDIRECT DETERMINATION OF AMINO-ACIDS

A PVC membrane electrode of the conventional type was prepared which i s selective for trinitrobenzenesulfonate (TNBS-). It showed a rapid Ne rnstian response within the TNBS- concentration range 1.0 x 10(-5) to 1.0 x 10(-2) M at 25 +/- 0.1 degrees C. The electrode was selective, p recise (RSD<0.87% for TNBS- and <1.32% for amino acids) and usable wit hin the pH range 2.5-12. The standard electrode potentials, E degrees, were determined at different temperatures and used to calculate the i sothermal temperature coefficient of the cell. Selectivity coefficient s for numerous compounds are given. The electrode has been used for th e direct determination of trinitrobenzenesulfonic acid in aqueous solu tions either by the standard additions method or by potentiometric tit ration against cetyltrimethylammonium bromide (CTABr) at pH 7. The ele ctrode has been also applied successfully for the indirect microdeterm ination of neutral, acidic and basic amino acids separately, and as bi nary or ternary mixtures of neutral amino-acids. Total amino acids wer e determined in urine samples.