Effect of the Pretreatment of Recast Nafion Membraneson Their Rejection of the Albumin Interferencein Anodic Stripping Voltammetry

Abstract

The title subject was examined using cadmium and lead as test analytes and differential pulse anodic stripping voltammetry as detection method. Ultrathin (ca. 0.3 µm) Nafion coatings were deposited on glassy carbon by electrostatic spray deposition. This technique proved far superior to evaporative casting with respect to the uniformity of the polymer layer. Overall, it was found that the pretreatment of the Nafion coating had a major effect on the extent of the albumin interference. Swelling of the Nafion coating in nitric acid and lithium hydroxide significantly reduced albumin interference, whereas treatment with sodium hydroxide and cesium hydroxide did not have an effect. Heat treatment (140 °C) of Nafion in the H+ form worsened the albumin interference, and the same trend was seen for the Na+ and Cs+ forms but not for the Li+ form. These results show that the degree of albumin interference is determined not only by the permeability of the coating but also by adsorption onto the outer surface of the membrane. The experimental results are explained in terms of the conformational changes of Nafion induced by the pretreatments.