Indirect Spectrophotometric Determination of Methimazole using Phenanthroline-Fe(II)

A novel method for the indirect determination of methimazole by spectrophotometry using phenanthroline-Fe(II) has been established.The results showed that in acid medium, Fe(III) could be reduced to Fe(II) by hydrosulfuryl(-SH) in methimazole molecule,and then using phenanthroline as chromogenic reagent of Fe(II), and the content of methimazole was determinated indirectly through determinating the content of Fe(II) by spectrophotometry. The various effect factors on the determination of methimazole by spectrophotometry using phenanthroline-Fe(II) were investigated in detail.The maximum absorption wavelength of chromogenic system was 509 nm, good linear relationship was obtained between the absorbance and the concentration of methimazole in the range of 0.0016 similar to 0.0064 mg/mL,the equation of the linear regression was A = 0.1942 + 64.598 rho (mg.mL(-1)),with a linear correlation coefficient was 0.9995.This proposed method had been applied to determinate of methimazole in real pharmaceutical,and the results agreed well with those obtained by pharmacopoeial method.