An ion-selective electrode for anion perchlorate in thick-film technology

The ionophore 1,4,7,10,13-penta(n-octyl)-1,4,7,10,13-pentaazacyclopentadecane (L-1) was used for the development of miniaturised perchlorate-selective electrodes in thick-film technology. Different PVC membranes containing L-1 and the plasticizers o-nitrophenyl octyl ether (NPOE), dibutyl phthalate (DBP), bis(2-ethylhexyl)sebacate (DOS) and dibutyl sebacate (DBS) were prepared and placed on a graphite working electrode manufactured by using thick film serigraphic technology. The perchlorate selective electrode containing DBS as plasticizer showed a potentiometric Nernstian response of -57 mV per decade in a range of perchlorate concentration from 1 x 10(-4) to 1 x 10(-1) M with a detection limit of 5 x 10(-5) M. The ion selective electrodes containing DBP and NPOE as plasticizers exhibit a working range from 6.3 x 10(-5) to 1 x 10(-1) M and 7.4 x 10(-5) to 1 x 10(-1) M for perchlorate, respectively, with a detection limit of ca. 2.2 x 10(-5) M. For all three electrodes a response time of ca. 5 s was found. The prepared electrodes do not show appreciable decay of the slope for at least 25 days. Potentiometric selectivity coefficients (log K-pot ClO4(-),(X)-) with respect to the primary anion perchlorate were evaluated using the fixed interference method. These coefficients are of the order of 10(-1.7) or smaller, indicating the relatively poor interference of the different anions studied.