Determination of pK a values of clinically important perfluorochemicals in nonaqueous media

Abstract

Perfluorochemicals (PFCs) are clinically and biotechnologically important species. In this work, the potentiometric titration method in nonaqueous media is proposed for the determination of acidity constant values of six different perfluorinated compounds. The saturated and nonsaturated perfluoroacids, perfluorocarnosine, and perfluoroalkyl-β-alanine were potentiometrically titrated in acetonitrile, N,N-dimethylformamide, acetone, ethanol, methanol, and pyridine with tetrabutylammonium hydroxide. The half-neutralization potentials and acidity constants of PFCs have been calculated from the titration curves by using the computerized derivative method. Except for RF-Carnosine, all of the potentiometric titration curves of the PFCs exhibited one stoichiometric and well-defined endpoints in all of the solvents employed. The reproducibility and sensitivity of the method were evaluated.