Sensitive spectrophotometric determination of trace-level Co2+ in water based on acetate enhanced catalysis of Co2+

摘要： A sensitive spectrophotometric method was developed for the determination of trace-level Co2+ in water based on the acetate enhanced catalytic decolorization of methylene blue (MB) with Co2+ as a catalyst and peroxymonosulfate (PMS) as an oxidizing agent. This indirect spectrophotometric method was easy to operate due to the strong absorption of MB at a maximum absorption wavelength of 664 nm with a molar absorptivity of 5.88 × 104 L mol?1 cm?1. Under the selected reaction conditions of 10.0 mg L?1 MB, 60.0 mg L?1 PMS and 100.0 mg L?1 Ac?, the depletion extent of MB was linearly correlated with the concentration of Co2+ from 0.20 to 7.0 μg L?1 (R2 = 0.986) and then from 7.0 to 50.0 μg L?1 (R2 = 0.991), with a detection limit (3 s/k) of 0.10 μg L?1. It was found that this method possessed excellent anti-interference capability to various coexisting ions including similar transitional metals. The developed method was used to determine the Co2+ concentration in practical samples with satisfactory results.