ADSORPTIVE STRIPPING VOLTAMMETRIC DETERMINATION OF ULTRA TRACE COBALT WITH ALIZARIN RED S MODIFIED CARBON PASTE ELECTRODE

A very sensitive and selective square wave cathodic adsorptive stripping (SWCAS) voltammetric method at modified carbon paste electrode (CPE) for determination of Cobalt(II) has been developed and evaluated. Square wave Cathodic Adsorptive Stripping Voltammetric (SWCASV) mechanism is proposed to interpret the amplified sensitivity. The procedure is based on the interfacial preconcentration of Cobalt (II) ion on Alizarin Red S through a surface coordination effect. The effect of various parameters such as medium, pH, accumulation potential, scan rate, accumulation time and ionic strength were tested to optimize the conditions for the determination of Cobalt(II) ion. The adsorbed form is reduced irreversible at optimal conditions viz; 0.15M Phosphate buffer (pH~9.5). Linear concentration range 2?10-12 - 6?10-11 M (0.00012 ? 0.00354 ng/mL (at 60s, can be determined successfully. The interferences of some common foreign species and some metal ions were studied. The high sensitivity and selectivity of this method were demonstrated by determination of cobalt in human hair and water samples.