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) was used for the development of miniaturised perchlorate-selective electrodes in thickfilm technology. Different PVC membranes containing L 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 to 1 x 10 M with a detection limit of 5 x 10 M. The ion selective electrodes containing DBP and NPOE as plasticizers exhibit a working range from 6.3 x 10 to 1 x 10 M and 7.4 x 10 to 1 x 10 M for perchlorate, respectively, with a detection limit of ca. 2.2 x 10 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 KClO4,X) with respect to the primary anion perchlorate were evaluated using the fixed interference method. These coefficients are of the order of 10 or smaller, indicating the relatively poor interference of the different anions studied.