Accumulation and voltammetric determination of cobalt at zeolite-modified electrodes

Chemically modified electrodes based on zeolite-containing graphite pastes were constructed and evaluated as sensor electrodes for the voltammetric determination of trace cobalt in solution. Zeolite molecular sieves with pore sizes of 3, 4, and 5 angstrom were all suitable for chemical deposition and subsequent voltammetric quantitation of trace Co(II). In order to cover a large range of parameters, the investigations were carried out using three zeolites (A, X, and Y), selected for their different cation-exchange capacities and ion-sieving properties. The analytical scheme, "preconcentration/voltammetric detection" for the determination of cobalt(II) species using zeolite-modified carbon paste electrodes (ZMCPE) was chosen. Compared to the corresponding unmodified electrodes, improvements in sensitivity were observed when using ZMCPEs due to analyte accumulation at the electrode's surface by ion exchange in zeolite particles. The detection limit obtained for Co(II) was 3 ppm following 15 min of chemical deposition. A good correlation was found between the results obtained by ion exchange voltammetry and conventional ion-exchange characterization.