Determination of Sulfate in Groundwater and Drinking Water by Inductively Coupled Plasma Atomic Emission Spectrometry

In view of the significant effect of sulfur ion on the determination of sulfate, the title method was proposed. When the mass concentration of sulfur ion was not greater than 0.10 mg·L^-1, the sample was directly introduced for analysis without pretreatment. When the mass concentration of sulfur ion was greater than 0.10 mg·L^-1, 50 mL of water sample was taken and mixed with 2 mL of nitric acid. The mixture was heated at 75℃ for 40 min, so that the sulfur ion was completely converted into hydrogen sulfide. The digestion solution was diluted to 50 mL with water, and determined according to the optimized working conditions of the instrument with sulfur analytical spectral line of 180.731 nm. It was shown that the mass concentrations of the sulfate were linearly related to their corresponding spectral line intensities in the range of 1.00-100.00 mg·L^-1, with detection limit (3s) of 0.07 mg·L^-1. Test for recovery was made by standard addition method on the actual samples, and detected amounts of sulfate were found in the range of 15.92-90.80 mg·L^-1, with values of recovery in the range of 96.8%-103% and RSDs (n=6) of the determined values in the range of 0.85%-2.8%.