Discrimination of methylammonium from organic ammonium ions using ion-selective electrodes based on calix[4]arene-crown-6 conjugates

Calix[4]-bis-2,3-naphtho-crown-6 can be used to discriminate between methyl ammonium and other organic ammonium ions. An electrode based on this ionoph ore, potassium tetrakis(p-chlorophenyl)borate (20 mol% relative to the iono phore) as an ionic additive and bis(2-ethylhexyl) sebacate as a solvent med iator in a poly(vinyl chloride) membrane matrix, displayed higher selectivi ty for methylammonium than for various other organic ammonium ions. However , there was considerable interference by inorganic cations, especially Cs+. Similar calix[4]arene-crown-6 conjugates, such as calix[4]-bis-1,2-benzo-c rown-6, calix[4]-bis-crown-6, 1,3-dioctyloxy-calix[4]arene-crown-6, 13-diis opropoxy-calix[4]arene-crown-6 and 1,3-dimethoxy-calix[4]arene-crown-6 were less effective in discriminating methylammonium.