Podand and macrocyclic amine receptors with urea functionalities for potentiometric detection of organic acids in HPLC

Ten synthetic receptors were tested in potentiometric coated wire electrodes. The electrodes were used as sensing devices in classical reversed phase HPLC determinations of dicarboxylic acids present in food materials. All receptors contained amine functionalities. Four of them were podand urea derivatives. The other six were macrocyclic polyamines with lipophilic groups. Three of them had urea functionalities in their side-chains. Glassy carbon (GC) substrate electrodes were coated with PVC-based “liquid membranes” containing plasticizers and receptors. All tested compounds strongly enhanced the detection limits for the dicarboxylic acids (low pg detection limits), in comparison to a non-specific electrode based on methyltridodecylammonium chloride (MTDDACl). Receptors of the podand urea type yielded high sensitivity, but the electrodes had a lower long-time stability (a few weeks) than the electrodes based on macrocyclic polyamines (at least 3 months).