A fast and environment-friendly method for determination of chemical oxygen demand by using the heterogeneous Fenton-like process (H2O2/Fe3−xCoxO4 nanoparticles) as an oxidant

•Use of the H2O2/Fe3−xCoxO4 system for COD determination.•A fast and environment-friendly method for oxidation of organic matter.•Good results in the study of a validation method.•Method can be applied in laboratory routine for COD determination in environmental samples.

An easy, fast and environment-friendly method for COD determination in water is proposed. The procedure is based on the oxidation of organic matter by the H2O2/Fe3−xCoxO4 system. The Fe3−xCoxO4 nanoparticles activate the H2O2 molecule to produce hydroxyl radicals, which are highly reactive for oxidizing organic matter in an aqueous medium. After the oxidation step, the organic matter amounts can be quantified by comparing the quantity of H2O2 consumed. Moreover, the proposed COD method has several distinct advantages, since it does not use toxic reagents and the oxidation reaction of organic matter is conducted at room temperature and atmospheric pressure. Method detection limit is 2.0 mg L−1 with intra- and inter-day precision lower than 1% (n=5). The calibration graph is linear in the range of 2.0–50 mg L−1 with a sample throughput of 25 samples h−1. Data are validated based on the analysis of six contaminated river water samples by the proposed method and by using a comparative method validated and marketed by Merck, with good agreement between the results (t test, 95%).

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