Highly sensitive and selective fluorescent assay for quantitative detection of divalent copper ion in environmental water samples

Abstract

It was found that Cu²⁺ has a great catalytic effect on p-cresol oxidation by hydrogen peroxide under alkaline conditions, leading to an intense fluorescence signal due to the fast formation of 2,2′-dihydroxy-5,5′-dimethylbiphenyl, an oxidation product of p-cresol. Investigation of the fluorescence spectra of the p-cresol–hydrogen peroxide system demonstrated the catalytic behavior of Cu²⁺. On this basis, a very simple, sensitive, and selective fluorescent method was established for the determination of trace copper in this study. Under the optimal conditions, the proposed system could respond down to 1.0 × 10⁻⁸ mol L⁻¹ of Cu²⁺ with a linear calibration range of 3.0 × 10⁻⁷ mol L⁻¹ to 5.0 × 10⁻⁵ mol L⁻¹. The relative standard deviation (RSD) was 2.1% for 7.0 × 10⁻⁶ mol L⁻¹Cu²⁺ (n = 15). The proposed method was successfully applied in the determination of trace Cu²⁺ in lake, river and swimming pool water samples with satisfactory results. The results obtained by the proposed method are in good agreement with those obtained by a conventional atomic absorption spectroscopy method.