Stopped-flow determination of 2-mercaptopyrimidines as inductors of the iodine-azide reaction

A stopped-flow method for the determination of 2-mercaptopyrimidine and its 14 derivatives by the iodine-azide has been elaborated. Spectrophotometric detection was applied and the decrease in the absorbance of the iodine-starch complex was monitored at 595 nm within 5 s. The effect of the concentration of the reagents on the rate of the reaction was investigated and a kinetic method for determination of compounds is proposed. 2-Mercaptopyrimidines can be determined at 10⁻⁶ to 10⁻⁵ mol L⁻¹ level and the relative standard deviation is below 1%. The elaborated method has been applied to the determination of 6-methyl- and 6-propyl-2-thiouracil in drugs.