Determination of Selenium in Water Samples by Using a Methylene Blue Kinetic Catalytic Spectrophotometric Method

Abstract

A kinetic catalytic spectrophotometric method, which was very sensitive and effective, was developed for the determination of selenium in water samples. It based on the catalytic effect of selenium on the reaction of methylene blue with sodium sulfide. A change in the absorbance of methylene blue with times at various concentrations of selenium were monitored, giving the “end point” (time) for each concentration of selenium. A plot of end point versus selenium concentration constituted a calibration graph, which was linear in a range of 2.5-30 ppb of selenium, with the correlation coefficient of 0.9992. The method was applied to determine the amount of selenium in the water sample containing 15 ppb of selenium, giving 91.84% recovery and the relative standard deviation of 2.27%. Compared with the hydride generation atomic absorption spectrometry method, this method is more sensitive for the determination of selenium in the water sample when the concentration of selenium is lower than 100 ppb.