Iodimetric determination of 2-mercaptopyrimidines

Abstract

A new method for the determination of 2-mercaptopyrimidines, using their reaction with iodine in neutral and alkaline medium, is presented. The determinability range in the volumetric titration, in phosphate buffer with starch as an indicator, was found to be equal to 40–1000 μmol for 2-mercaptopyrimidine (I) and 100–2000 μmol for 2-mercapto-4-methylpyrimidine (II), and 200–2000 μmol for 4,6-dimethyl-2-mercaptopyrimidine (III). In the volumetric titration in alkaline medium, with the potentiometric end-point detection, the determinability range is 50–250 μmol for 2-mercapto-4-methylpyrimidine (II), 50–500 μmol for 4,6-dimethyl-2-mercaptopyrimidine (III), 20–250 μmol for 4,5-diamino-2,6-dimercaptopyrimidine (IV), and 20–1000 μmol for 2-thioorotic acid (V). In the coulometric titration, using the biamperometric end-point detection, 0.1–4.0 μmol of 2-mercaptopyrimidine (I) and 0.1–5.0 μmol of 2-thioorotic acid (V) were successfully determined.