Novel potentiometric membrane sensor for selective determination of aluminum(III) ions

A poly(vinyl chloride) matrix membrane sensor incorporating 7-ethylthio-4-o xa-3-phenyl-2-thioxa-1,2-dihydropyrimido-[4,5-d]pyrimidine (ETPTP) ionophor e exhibits good potentiometric response for Al3+ over a wide concentration range (10(-5) to 10(-1) M) with a dope of 19.5 mV per decade. The sensor re sponse is stable for at least 1 month. Good selectivity for Al3+ in compari son with alkali, alkaline earth, transition and heavy metal ions and minima l interference are caused by Hg2+ and Pb2+ which are known to interfere wit h other aluminum membrane sensors. The ETPTP-based sensor is suitable for u se in aqueous solutions of pH 2.25-3.25 and in partially non-aqueous medium with up to 15% (v/v) organic content. The proposed sensor is used for pote ntiometric titration of HPO42- with Al3+ and for direct potentiometry of Al 3+ content of some rocks. (C) 2001 Elsevier Science B.V. All rights reserve d.