Urea-functionalized calix[4]arenes as carriers for carbonate-selective electrodes

A new PVC membrane electrode for CO32− anion based on urea-functionalized calix[4]arenes (I–IV) as neutral ionophores is prepared. Of the various membranes prepared, the membrane based on bis-urea calix[4]arene I exhibits a linear stable response over a concentration range (5.0 × 10−4 to 1.0 × 10−1) with a slope of −29.2 mV per decade and a detection limit of 1.2 × 10−4 M, and the best selectivity for CO32− anion [ K T C O 2 J pot = 1.9 × 10 − 2 ( sa l − )       and       2.1 × 10 − 2 ( I − ) ] over salicylate and iodide.