DIFFERENTIAL-PULSE ADSORPTIVE STRIPPING VOLTAMMETRIC DETERMINATION OF TYROSINE AND HISTIDINE AT A HANGING MERCURY DROP ELECTRODE AFTER COUPLING WITH DIAZOTIZED SULFANILIC ACID

Tyrosine and histidine can be determined in the range between 5.0 X 10(-8) and 1.0 X 10(-6) mol dm-3 by differential-pulse adsorptive stripping voltammetry after derivatization with diazotized sulphanilic acid (DSA) at pH 9.2 for 1 h. The amount of DSA added has to be controlled as, in large excess, DSA competes with the derivatives for adsorption on the electrode surface. The relative standard deviation (six determinations at the 2.5 X 10(-7) mol dm-3 level) was typically 5%.