Nephelometric Determination of Traces of Selenium with Thiourea as Reductant

In an acidic medium of 0.3 mol·L-1 HCl and in the presence of glycerol as stabilizer,Se(Ⅳ) was reduced to elemental state by excess of thiourea and kept in stable and homogeneous suspension.Absorbance value of the turbid solution was measured at the wavelength of 294 nm,and linear relationship between values of absorbance and mass concentration of Se(Ⅳ) was obtained in the range within 25 mg·L-1.Detection limit (3s/k) of the method found was 0.047 1 mg·L-1.The proposed method was used in the determination of selenium in samples of selenium-fortified nutritious salt and health-balance salt,the results obtained were in conformity with the results found by fluorophotometry,and the average value of RSD′s (n=5) and value of average recovery found were 2.4% and 99.1% respectively.