Automatic and Matrix Interference-Free Acid–Base Titration by Coupling CO₂ Vapor Generation with Microplasma Carbon Optical Emission Spectrometry

Acid–base titration of complex samples is conducive to the rapid evaluation of the degree and risk of environmental pollution to some extent. However, the traditional titration methods usually suffer from serious interference. Herein, an automatic acid–base titration method coupling miniature point discharge optical emission spectrometry (μPD-OES) with CO₂ vapor generation was described for the precise, sensitive, and matrix interference-free acid–base titration of complex samples, particularly those with high color intensity, salinity, and turbidity such as wastewater and soil samples. In this work, acid–base titration was carried out in a chemical vapor generator where CO₂ was generated through the addition of HCl or NaHCO₃, thus enabling efficient separation of CO₂ from a complex matrix. The generated CO₂ was subsequently swept into the miniaturized point discharge for excitation and further detection by μPD-OES, where the carbon atomic emission at 193.0 nm was monitored. According to the consumed volume and concentration of HCl, accurate and automatic measurements of OH^–, CO₃^2–, and HCO₃^– can be accomplished. The proposed method possesses a high sensitivity of μPD-OES for the detection of CO₂ with a relative standard deviation of below 3.0%. Moreover, the proposed system not only retains several unique advantages of accuracy, simplicity, and elimination of the use of complicated, expensive, and high power-consumption instruments but also alleviates the color and turbid interference from complex samples such as dyeing wastewater samples, oilfield water samples, and soil samples. It retains a promising potential application for titration analysis of other samples such as sludge, sediment, and landfill leachate.