Comparative study of polyether-type neutral carriers for the potentiometric sensing of guanidinium ions

Abstract

Poly(vinyl chloride) membrane electrodes, based on dibenzo-27-crown-9 [(DB27C9)(sensor 1)], dibenzo-30-crown-10 [(DB30C10)(sensor 2)], bis(metaphenylene)-26-crown-8 [(BMP26C8)(sensor 3)], 1,11-bis(2-benzyloxy-5-formylphenoxy)-3,6,9-trioxaundecane (sensor 4) and 1,11-bis(2-hydroxy-5-formyl-phenoxy)-3,6,9-trioxaundecane (sensor 5), in conjunction with various solvent mediators and anion excluders, have been tested for their response to guanidinium ions and other inorganic and organic species. Of the various systems studied, the best over-all guanidinium ion-selective electrode (ISE) was based on sensor 3(BMP26C8) with either dibutyl phthalate or dioctyl adipate as solvent mediators, and with or without guanidinium tetraphenylborate or guanidinium tetrakis(4-chlorophenyl)borate as the anion excluder. In most instances, the incorporation of the anion excluders in the membrane improved the selectivity towards guanidinium over inorganic cations and lowered the membrane resistance. In turn, the guanidinium ISEs based on the two disubstituted diphenyl ethers (sensors 4 and 5) were superior to those based on sensors 1(DB27C9) and 2(DB30C10). The selectivity coefficients for ten potential inorganic and organic interferents, and the lifetimes, resistances and response times of the electrodes are reported.