Estimation of the Total Phenol Content during Photolysis of Sulfamethoxazole in an Aqueous Medium

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Abstract In natural and artificial water bodies, photolysis is the primary process that determines the transformation and fate of many pharmaceuticals. However, there is a lack of information on the degradation products of sulfonamide antibiotics and their toxicity. Phenols are potential products of pharmaceutical contaminants transformation and pose a threat to human health. This paper presents results of an experimental study of sulfamethoxazole phototransformation in water. The irradiation experiments were carried out in a stationary photoreactor using KrCl (λ = 222 nm), XeBr (282 nm), and XeCl (308 nm) excilamps and an OUVb-04 bactericidal irradiator (λ = 180–275 nm) as sources of UV radiation. The total phenol content in sulfamethoxazole photoproducts is determined using the colorimetric method with the Folin–Ciocalteu reagent. The changes observed in the absorption and fluorescence spectra after irradiation of aqueous sulfamethoxazole solutions are described in detail. The formation of three fluorescent photoproducts is shown; one of them turns out to be stable and is accumulated in the solution regardless of the chosen UV radiation source. The total phenol content increases after UV irradiation. In particular, the total phenol content after 128 min of exposure to a KrCl excilamp is four times higher than the initial value and amounts to 331.89 mg GAE/g. The results can be of interest for studying the mechanism of sulfonamide degradation, identifying toxic products of degradation, and evaluating their antioxidant activity.

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