Poly(binaphthyl-20-crown-6) as receptor based molecular selective potentiometric electrodes for catecholamines and other 1,2-dihydroxybenzene derivatives

Abstract

A novel type of poly(crown ether) electrode that is capable of selectively determining some 1,2-dihydroxybenzenes has been developed. A lipophilic macrocyclic crown ether, binaphthyl-20-crown-6, is electrochemically deposited on a platinum disc electrode. The film obtained is used as a sensory element for a potentiometric electrode for the determination of some neurotransmitters, namely, catecholamines. The new electrode is also capable of discriminating the steric shapes of 1,2-dihydroxybenzene moieties. The response of the new electrode is based on the principle of ‘host-guest’ chemistry. The potentiometric response is dependent on the pH of the solution and the nature of the buffer medium. The new sensor electrode has a useful analytical range of 1·5 × 10 −8 M-2 × 10 −5 M with a linear dynamic range between about 1 × 10 −7 M-5 ×10 −4 M with a ‘super-Nernstian’ slope of 110–130 mV/decade. The detection limit in phosphate buffer (0·1 M, pH 9·4) is ca. 3 × 10 −8 M for catecholamine. The sensor electrode is virtually insensitive towards interference from most inorganic ions and circumvents the interference from ascorbic acid, which is often found using amperometric methods in biological samples. A partial response mechanism of the present electrode is discussed, supported by results of electron dispersive analysis by x-rays (EDAX).