Voltammetric detection of inorganic phosphate using ion-channel sensing with self-assembled monolayers of a hydrogen bond-forming receptor

A voltammetric ion-channel sensing for phosphate based on gold electrodes modified with the self-assembled monolayers of a bisthiourea receptor was developed to detect phosphate. The working principle of this voltammetric sensor conceptually mimics that of ligand gated ion-channel proteins, as to chemically stimulated changes in membrane permeability. The response to analytes is based on the change in electron transfer rate constant of the redox reaction of [Fe(CN)(6)](4-/3-) marker, before and after binding of phosphate to the receptor on the electrode surface; where the electrostatic repulsion between a phosphate-receptor complex and the marker induced the decrease in the rate constant. In a solution of pH 7.0, a high selectivity was observed for phosphate and the sensor was virtually insensitive at all to many of other anions, such as SO42-, AcO-, NO3-, and Cl-. The sensor response was obtained with phosphate concentrations above 5.0 x 10(-4) M using cyclic voltammetry and differential pulse voltammetry. (C) 2002 Elsevier Science B.V. All rights reserved.