Simple Electrochemical Detection Method Employing a Hydrogel Soft Matrix: Application in Tap Water

Abstract

The proposed method implies the electrochemical detection of an analyte preloaded in a hydrogel. In order to evaluate the potential application of this method, arsenic detection in tap water was performed. Polymeric hydrogels bearing cationic groups poly(N-isopropyacrylamide)-co-3-(acrylamidopropyl)trimethylammonium chloride were used to sorb arsenic ions, at basic pH, from the real and synthetic stock samples. The concentration of arsenic was electrochemically determined using the loaded hydrogel and a modified glassy carbon electrode. Employing a cationic hydrogel, the peak current for the arsenic oxidation was ca. 8 times higher than the peak current measured using poly(N-isopropyacrylamide), a neutral hydrogel, indicating a strong electrostatic interaction between the polymeric cationic groups and arsenite anions. By using this method, values of arsenic comparable to those measured by Atomic Absorption Spectroscopy were obtained for tap water of small cities in Argentina. These results suggest that this new and easy method is suitable to sense a threshold limit of arsenic in real samples since the features of the hydrogel allow the arsenite loading into the matrix. Besides the cationic hydrogels could be employed to sampling on-field and to build a portable analysis system.