Use of two ion-selective electrode-containing cells for potentiometric titration of hexadecylpyridinium bromide

Hexadecylpyridinium bromide (HDPBr) has been titrated potentiometrically with a standard solution of sodium tetraphenylborate(III)(NaTPB) in a cell containing two membrane electrodes that are selective for hexadecylpyridinium (HDP+) and tetraphenylborate(III)(TPB–) ions. Titration curves with sharp peaks or troughs were obtained, enabling the equivalence points to be located precisely. The solubility product of the precipitated ion pair, HDP-TPB, was determined conductimetrically and was used to calculate the equilibrium constant of the reaction between HDPBr and NaTPB.