Chemiluminescence of cobalt(II)–hydrogen peroxide–hydrogencarbonate in the absence of luminescent reagents

A novel chemiluminescence (CL) system, cobalt(II)–hydrogen peroxide–hydrogencarbonate without luminescent reagents, was described. When cobalt(II) was injected into mixed solution of 0.4 mol l−1 hydrogencarbonate and 0.01 mol l−1 hydrogen peroxide in a flow injection system, CL occurred, which was significantly enhanced when rhodamine B coexisted. The CL emission intensity was found correlation with the concentration of cobalt(II) in the range of 2.0×10−9–1.0×10−5 mol l−1 with a detection limit of 1.2×10−9 mol l−1 cobalt(II). The relative standard derivative (RSD) for 5.0×10−7 mol l−1 cobalt(II) was 1.6% based on nine repetitive measurements. In addition to cobalt(II), other metal ions were also investigated, and only chromium(III) gave out measurable CL emission. The possible mechanism was discussed based on the CL emission spectrum.