Abstract
The rapid d.c. polarography of 2,4,6-trinitrobenzene-1-sulphonic acid and its derivatives with serine (I), threonine (II), glycine (III) and histidine (IV) revealed a 3-wave reduction and a marked pH dependence of the reduction potential. The polarographic waves of the derivatives (2.5 × 10
−4 M) showed appreciable changes when sulphite ions were present, with the development of a new wave at more negative potential in ⩾0.01 M sulphite solutions at pH 7.0. The
E
1/2 values of these waves in pH 7.0 supporting electrolyte were: (I) −1000; (II) −1007; (III) −1021; (IV) −949 mV (vs. Ag/AgCl, sat. KCl). These waves were used to determine the amino acids investigated (1–4 × 10
−4 M) in the presence of excess of 2,4,6-trinitrobenzene-1-sulphonic acid, with good precision (2%).