POLY(BINAPHTHYL-20-CROWN-6) AS RECEPTOR-BASED MOLECULAR SELECTIVE POTENTIOMETRIC ELECTRODES FOR CATECHOLAMINES AND OTHER 1,2-DIHYDROXYBENZENE DERIVATIVES

A novel type of poly(crown ether) electrode that is capable of selecti vely determining some 1,2-dihydroxybenzenes has been developed. A lipo philic macrocyclic crown ether, binaphthyl-20-crown-6, is electrochemi cally deposited on a platinum disc electrode. The film obtained is use d as a sensory element for a potentiometric electrode for the determin ation of some neurotransmitters, namely, catecholamines. The new elect rode is also capable of discriminating the steric shapes of I,2-dihydr oxybenzene moieties. The response of the new electrode is based on the principle of 'host-guest' chemistry. The potentiometric response is d ependent 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 x 10(- 8) M-2 x 10(-5) M with a linear dynamic range between about 1 x 10(-7) M-5 x 10(-4) M with a 'super-Nernstian' slope of 110-130 mV/decade. T he detection limit in phosphate buffer (0.1 M, pH 9.4) is ca. 3 x 10(- 8) M for catecholamine. The sensor electrode is virtually insensitive towards interference from most inorganic ions and circumvents the inte rference from ascorbic acid, which is often found using amperometric m ethods in biological samples. A partial response mechanism of the pres ent electrode is discussed, supported by results of electron dispersiv e analysis by x-rays (EDAX).