Determination of Co2+ based on the cobalt(II)-catalyzed electrochemiluminescence of luminol in acidic solution

In this paper, the electrochemical behavior of luminol in weakly acidic solution was studied. It is found that Co2+ remarkably enhances the electrochemiluminescence (ECL) of luminol in citric acid–sodium citrate buffer solution (pH = 4.0) when a pulse potential (−1.8 to +1.0 V, versus Ag/AgCl) is applied to the Pt electrode. The selectivity for Co2+ is very good because most of the other water-soluble metal ions do not interfere. A sensitive and selective ECL method for determination of Co2+ is proposed. After optimization of the reaction conditions and electrochemical parameters influencing the relative ECL intensity, the linear range responding to Co2+ is 5.0 × 10−12 to 1.0 × 10−7 mol/L, and the detection limit is 2.0 × 10−12 mol/L. The relative standard deviation for 5.0 × 10−10 mol/L cobalt(II) is 3.7% (n = 11).