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

Abstract

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.