Investigation of ion-selective electrodes based on quanternary phosphonium salts: Part 3. An Ion-Selective Electrode for Hexafluorophosphate

A hexafluorophosphate-selective electrode based on the tetradecylphosphonium hexafluorophosphate(V) ion-pair complex in a PVC membrane is described. The active material is a white powder; its solution in dibutyl phthalate was used for the electrode membranes. The composition of the tetradecylphosphonium hexafluorophosphate was identified as its infrared and ³¹P-n.m.r. spectra. The calibration curves for the elelctrode were investigated and interpreted with respect to the hydrogen fluoride concentration of the sample solution. It is shown that the hydrolysis of hexafluorophosphate depends on the hydrofluoric acid content of the solution. The lifetime of the electrodes is about one month and the limits of detection vary from aobut 10^?7 mol 1^?1 to 10^?6 mol 1^?1 with 0–1 mol 1^?1 hydrofluoric acid present.