CHARACTERIZATION OF DI(2-ETHYLHEXYL)THIOPHOSPHORIC ACID BY POTENTIOMETRIC TITRATION AND CAPILLARY ZONE ELECTROPHORESIS

The acidity constant of di(2-ethylhexyl) thiophosphoric acid (DEHTPA) was investigated using potentiometric measurements with a pH glass ele ctrode. Owing to the low solubility of DEHTPA in pure water, its conce ntration and acidity constants were determined by linearised pH-metric titration in 16.7% ethanol, A K-a value of (2.39 +/- 0.08) x 10(-4) w as obtained. Quantitative determination of DEHTPA was performed by cap illary zone electrophoresis (CZE) with carbonate buffer (pH 11.0) as a background electrolyte, operating at -20 kV with direct UV detection at 210 nm. The migration time was 8.97 min and the detection limit was 5 ppm.