Potentiometric monitoring of cobalt in beer sample by solid contact ion selective electrode

A new solid contact cobalt selective electrode was constructed with 4-tert-butylthiacalix[4]arene as ionophore. The best performance was observed with the membrane having an ionophore/polyvinyl chloride/sodium tetraphenylborate/nitrophenyl octyl ether ratio of 3.5:33:1.5:62 (w/w; mg). The electrode, under steady-state conditions, exhibited a working concentration range of 1 × 10^-1 - 1 × 10^-6 mol/L with a near-Nernstian slope of 25.3 mV/decade and a detection limit of 3.5 × 10^-7 mol/L. The electrode had a very short response time (<10 seconds) and good reproducibility at a working pH range of 4.0-6.5. The electrode was used for 4 months without any significant change in its sensitivity. The potentiometric performance of the electrode in partially nonaqueous medium [up to 20 % (v/v) alcohol] was found satisfactory. The performance of the prepared electrode for the analysis of beer samples using direct potentiometric method is very encouraging.