Pre-concentration of cobalt by clinoptilolite modified with N,N -1,2-cyclohexylene bis(salicylidene amine)

A simple, highly sensitive, accurate and selective method for pre-concentration and determination of trace amount of Co2+ from aqueous media is proposed. The procedure is based on the adsorption of Co2+ clinoptilolite modified by N, N’-1,2-cyclohexylene bis(salicylidene amine) at pH 6 [1, 2]. The retained cobalt on the column was eluted with 5 ml 1 M HNO3 in ethanol and measured by flame atomic absorption spectrometry. The influence of pH, type of eluent, flow rate of the sample solution and eluent, volume of eluent and the presence of other cations were investigated. A preconcentration factor of 140 can be achieved by passing 700 ml of sample through the column. The limit of detection (LOD) of the proposed method defined as three times the standard deviation of the blank (3s) was 0.12 ng ml-1 and the results obtained on 10 replicate measurements revealed a RSD of 1.1%. The proposed method was applied to the determination of cobalt in water samples [3, 4].