Fast Detection of Carbonate and Bicarbonate in Groundwater and Lake Water by Coupled Ion Selective Electrode

The content of carbonate (HCO3−) and bicarbonate (CO32−) in the freshwater is an important characteristic of the geochemical environment. However, the environmental factors affect the concentration of two ions easily during the process of sampling, transportation and storage. It is a worldwide problem to determine the real content of carbonate and bicarbonate ions in the freshwater. To solve this problem, a new approach was proposed for the rapid determination of carbonate and bicarbonate ions in groundwater and lake water through a pH electrode combined with a CO2 electrode. The results showed that the liner range of bicarbonate was 0.027–570 mg L−1 and that of carbonate was 1.25 × 10−8−39.7 mg L−1. In the most case, the coexisting cation, anion and weak acid (K+, Na+, Mg2+, Cl−, SO42− < 100 mg L−1, HSO3−, NO2−, HOAc < 50 mg L−1) did not interfere with the analysis. The method was validated for real water samples and the recoveries were in the range of 95.2%–99.2% with the relative standard deviations (RSDs) of 2.6%–3.7%. The accuracy of the method was proved to be well matched with acid-base titration. However, the electrodes were temperature sensitive, so the standard solution and samples should be measured at the same temperature. In general, the method was sensitive, fast, economical, easy to carry and simple to operate, which was appropriate for rapid detection of bicarbonate and carbonate ions in freshwater in field. The method was applied in determination of bicarbonate and carbonate ions in the groundwater and lake water in Qinghai Province, China and it was found that the pH values in the groundwater samples from Haidong area were from 6.4 to 7.4, with the HCO3− content of 234–4096 mg L−1 and CO32− content of 0.16–1.89 mg L−1, and the samples from Qinghai Lake had a pH about 8.7, with the HCO3− content of 1.36–1.86 g L−1and CO32−- content of 32.3–43.9 mg L−1, which was consistent with the previous results.

Graphical AbstractThe content of carbonate and bicarbonate in the freshwater varies along with the change of temperature, air pressure and other environmental factors, so it is difficult to determine their real content. A new approach was proposed for quick detection of carbonate and bicarbonate ions in groundwater and lake water through a pH electrode combined with a CO2 electrode.Figure optionsDownload as PowerPoint slide