Electrochemical Preparation and Characterization of an Anion-Permselective Composite Membrane for Sensor Technology

We describe the construction and characterization of an ultrathin-film composite membrane (UTFCM) prepared by electropolymerization of a thin coating of poly[1-methyl-3(pyrrole-1-ylmethyl) pyridinium] (poly-MPP), across the surface of a microporous support membrane. The ion-exchange properties of the UTFCM were investigated by testing the permeability of the membrane for electroactive anions and cations. Both polycarbonate and alumina microporous membranes were employed as support membranes. The alumina supports proved superior in that thinner anion-permselective poly-MPP coatings could be obtained. These thinner coatings allowed for fast permeation of anions while still blocking the passage of cations. Alumina-poly-MPP composite membranes were used to construct a nitrate sensor in which the UTFCM separates the analyte solution from an internal sensing solution which contained the enzyme nitrate reductase and an electrocatalyst (methyl viologen).