Electrochemical preparation and characterization of an anion-permselectivecomposite membrane for sensor technology

We describe the construction and characterization of an ultrathin-film comp osite membrane (UTFCM) prepared by electropolymerization of a thin coating of poly[1-methyl-3(pyrrole-1-ylmethyl) pyridinium] (poly-MPP), across the s urface of a microporous support membrane. The ion-exchange properties of th e UTFCM were investigated by testing the permeability of the membrane for e lectroactive 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 obt ained. These thinner coatings allowed for fast permeation of anions while s till blocking the passage of cations. Alumina-poly-MPP composite membranes were used to construct a nitrate sensor in which the UTFCM separates the an alyte solution from an internal sensing solution which contained the enzyme nitrate reductase and an electrocatalyst (methyl viologen).