Solid-contact Acetate-selective Electrode Based on a 1,3-bis(carbazolyl)urea-ionophore

The construction and study of solid-contact acetate-selective electrodes is described using a 1,3-bis(carbazolyl)urea derivative as a neutral hydrogen-bonding ionophore and poly(3,4-ethylenedioxythiophene) as the solid contact. It was shown recently that this ionophore binds acetate (logK(ass)=4.98) that is used as primary ion in this study. The electrodes show linearity over the activity range of 10(-4.50)-10(-1.10) with a sub-Nernstian slope of -51.3 mV per decade and a detection limit of 10(-5.00). The anion-selectivity pattern of these electrodes deviates markedly from the Hofmeister pattern. When adding ionophore to the membrane the logarithm of the selectivity coefficient (logK) for SCN- decreased from 6.5 to 1.2, logK for I- decreased from 5.7 to 0.9, logK for NO3- decreased from 4.3 to 0.6 and logK for Br- decreased from 3.3 to 0.1. The selectivity coefficients of hydrophilic anions such as Cl-, F-, HPO42-, and SO42- are significantly lower than in case of the ionophore-free membrane. It was discovered that the constructed electrodes are also relatively selective to bicarbonate. This work is an important step towards the further development of solid-contact anion-selective electrodes.