Spectrophotometric determination of silicon in steel with rhodamine B-hetersilicomolybdic acid system in microemulsion medium

A method for determination of silicon in steel samples by colour reaction of rhodamine B-hetersilicomolybdic acid in O/W nonionic microemulsion medium(OP/-nC5H11OH/n-C7H16/H2O) was established.In the optimal experimental conditions,the maximum absorption wavelength of the complex formed by rhodamine B and hetersilicomolybdic acid is at 590 nm.Linear regression equation is y=0.278 1x-0.012 4.Beer′s law is obeyed in 0.006-0.07 μg/mL for silicon.The detection limit is 2×10-6 g/L and the apparent molar absorptivity is 3.89×105 L·mol-1·cm-1.The interferences from P(Ⅴ) and As(Ⅴ) were removed by adding tartaric acid.The method has been applied in the determination of silicon in steels with RSD of 1.6 %-2.1 %,and the results were consistent with certified values.