Application of Automatic Potentiometric Titrator in Continuous Titration of Six Indices in Groundwater

Abstract

BACKGROUND The analysis of six indices (pH, total alkalinity, chloride ion, calcium ion, magnesium ion and sulfate radical) in underground water needed to be sampled separately for each index. The steps were tedious with low efficiency. Furthermore, the total alkalinity, chlorine ion, calcium ion, magnesium ion and sulfate radical usually used manual visual titration, resulting in manual operation error, poor precision, and inaccuracy. OBJECTIVES To establish an accurate and rapid method for the analysis of six indices in underground water. METHODS The method established and described in this paper only needed two samples and the Automatic Potentiometric Titrator could determine the end point automatically. The Automatic Potentiometric Titrator could accurately control the addition of standard solution to 0.1 μL, and eliminate mutual interference by adjusting the detection order, acidity and the addition of a masking agent. RESULTS The recoveries of this method are 93.5%-120.0%, and the relative standard deviations (RSDs, n=10) are 0.18%-11.33%. CONCLUSIONS The results obtained by potentiometric titration had better parallelism and stability, especially when the measured water samples were more turbid or colored.

Keywords

• automatic potentiometric titrator
• groundwater
• continuous titration
• titration endpoint
• masking agent