Estimation of thioacetamide using photochemical exchange reaction of sodium nitroprusside

A simple, sensitive, inexpensive, reliable and quantitative method has been developed for the determination of thioacetamide using sodium nitroprusside (SNP) as a spectroscopic probe. This method indicates that the sodium nitroprusside can react with the thioacetamide to form a colored product in the light reaction. Sodium nitroprusside is a photolabile complex and it undergoes photochemical ligand exchange reactions rapidly. The absorbance of the product is measured at the maximal absorption wavelength of 540.8 nm, and the amount of thioacetamide can be calculated based on this absorbance by using calibration curve. The good linear relationship of the concentration of thioacetamide versus absorbance is observed with a linear range of 1.48 x 10-4 – 9.5 x 10-4. The linear regression equation is A = 0.017x + 0.006, with the correlation coefficient of 0.999. The effects of different parameters like pH, change of concentration of sodium nitroprusside, concentration of ligands, light intensity etc. on percentage error were investigated. The efforts were made to minimise the percentage error and some optimum conditions were obtained. The progress of photochemical reaction for sample solution has been observed spectro-photochemically and the product was isolated and characterized. A tentative mechanism for this reaction has been proposed.