Differential kinetic determination of cobalt and vanadium with thermal-lens monitoring

On the example of a model indicator reaction of oxidation of cobalt (II) and vanadium (IV) ions by a complex of iron (III) with 1,10-phenantroline, resulting in the formation of tris-(1,10-phenantroline) iron (II), an application of thermal-lens detection of analytical signal with differential kinetic methods is reported. For the simultaneous differential kinetic determination of cobalt (II) and vanadium (IV) with thermal-lens signal detection (514.5 nm, 35.5 mW), the achieved limit of detection (LOD) is 2 ng/ml for both metals, matching the respective values for individual determination. In comparison to spectrophotometric techniques, the effect of synergy, which reduces the sensitivity of detection in the system, is found to be negligible. In general, the sensitivity of differential kinetic determination of cobalt (II) and vanadium (IV) with thermal-lens registration of signal is superior to the analogous procedure with spectrophotometric control of the reaction velocity by two orders of magnitude.