Limit of detection in barium sulphate gravimetry for water analysis
Abstract
Sulphate ions in the 1–5 mg l–1 SO42– range can be determined gravimetrically in 200-ml samples using a large excess of barium chloride. From ten determinations at each of three concentration levels of standard sodium sulphate solution, the analytical calibration function calculated by weighted least squares is xc(mg l–1 SO42– found)=(0.093 ± 0.064)+(1.008 ± 0.039)c(mg l–1 SO42– added) with 95% confidence intervals. The limit of detection is cL= 1 mg l–1 SO42–(k= 3). A systematic approach is suggested for determining the limit of detection, by considering the variance of both the blank and the calibration function.