A new method for the FIA of acid and base samples in nonaqueous solvents was proposed. This analysis, using a “pH” buffer solution and a glass electrode, is based on the detection of pH changes in the buffer solution by the glass electrode when the sample acids or bases are mixed with the buffer solution. The sample (200 µ1) injected into an ethanol stream was merged with the stream of the buffer solution (e.g. 5x10–3 M tetrabutylammonium butyrate-5x10–3 M butyric acid, M=moldm–3) containing 0.1 M lithium chloride. The potential change of the glass electrode was observed as a peak-shaped signal, and a linear relationship between the peak height and the concentration of samples was observed. Many organic acids as well as aliphatic and some aromatic amines were determined by the proposed FIA titration of ca. 40 samples/h with less than 0.5% relative standard deviation. The sensitivity of the proposed method was discussed in connection with the relative acidities (apparent pKa's) of samples to those of the buffer acids. The proposed method was successfully applied to the determination of the total alkalinity in lubricating oils.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry