Coated-wire organic ion-selective electrodes in titrations based on ion-pair formation

Abstract 1-(Ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex) is recommended as a titrant for the determination of singly-charged acidic anthraquinone dyestuffs. Other cationic titrants such as cetylpyridinium bromide or cetyltrimethylammonium bromide can be used for titrations of dilute aqueous solutions (about 10 −4 M) or in the presence of additional solvent (5% n-propanol). An aluminium wire electrode coated with a PVC membrane plasticized with 2-nitrophenyl alkyl ether (where alkyl is either n-octyl or 2-ethylhexyl) is used for end-point indication. Characteristic data for the potentiometric titration curves and a statistical evaluation of results are reported.