CHLORIDE-SELECTIVE ELECTRODES BASED ON MERCURY ORGANIC-COMPOUNDS AS NEUTRAL CARRIERS

Mercury organic compounds incorporated in solvent polymeric membranes act as neutral carriers for chloride. In sharp contrast to classical anion exchangers, membranes containing {mu-[4,5-dimethyl-3,6-bis(octyloxy)-1,2-phenylene]}bis(trifluoroacetato-O)dimercury (ETH 9009) or tetrakis[mu-(dimethyl sulphoxide-O:O)]bis{mu-[hexafluoro-pentanedionato(2-)-O:O']}bis{mu-[4,5-dimethyl-3,6-bis(octyloxy)-1,2-phenylene]}tetramercury (ETH 9011) as anion carriers, tridodecylmethylammonium chloride as additive, bis(2-ethylhexyl) sebacate (DOS) as plasticizer and poly(vinyl chloride) as membrane matrix show a preference for chloride over bromide, thiocyanate, perchlorate, nitrate and salicylate. Ion-selective electrodes with such membranes displayed a Nernstian electrode function for chloride in the concentration range 10(-5)-0.1 M. For the more concentrated NaCl solutions, the potential drift of the cell assembly was < 1.5 mV h-1 and the response time (t90%) was < 10 s. In 0.01 M NaCl, e.m.f. repeatabilities were found to be +/- 0.16 and +/- 0.29 mV for ISEs based on ETH 9009 and ETH 9011, respectively. C-13 NMR studies showed ETH 9011 to interact with chloride and thiocyanate, forming 4: 1 complexes, but not with perchlorate and nitrate.