IODIMETRIC DETERMINATION OF 2-MERCAPTOPYRIMIDINES

A new method for the determination of 2-mercaptopyrimidines, using the ir reaction with iodine in neutral and alkaline medium, is presented. The determinability range in the volumetric titration, in phosphate bu ffer with starch as an indicator, was found to be equal to 40-1000 mu mol for 2-mercaptopyrimidine (I) and 100-2000 mu mol for 2-mercapto-4- methylpyrimidine (II), and 200-2000 mu mol for 4,6-dimethyl-2-mercapto pyrimidine (III). In the volumetric titration in alkaline medium, with the potentiometric end-point detection, the determinability range is 50-250 mu mol for 2-mercapto-4-methylpyrimidine (II), 50-500 mu mol fo r 4,6-dimethyl-2-mercaptopyrimidine (III), 20-250 mu mol for 4,5-diami no-2,6-dimercaptopyrimidine (IV), and 20-1000 mu mol for 2-thioorotic acid (V). In the coulometric titration, using the biamperometric end-p oint detection, 0.1-4.0 mu mol of 2-mercaptopyrimidine (I) and 0.1-5.0 mu mol of 2-thioorotic acid (V) were successfully determined. (C) 199 8 Elsevier Science B.V. All rights reserved.