Direct photolysis of benzoylecgonine under UV irradiation at 254 nm in a continuous flow microcapillary array photoreactor

Benzoylecgonine (BE) is the major metabolite of cocaine and a contaminant of emerging concern often detected in sewage treatment plant (STP) effluents and surface waters. In this study, an innovative microcapillary film (MCF) array photoreactor made of fluoropolymer material was used to determine the direct photolysis quantum yield at 254 nm of benzoylecgonine. The photolysis quantum yield of BE was found to be (6.22 ± 0.19) ⋅ 10−3 mol ein−1. The proposed methodology was validated by estimating the quantum yield of caffeine (7.48 ± 0.64) ⋅ 10−4 mol ein−1, which was found in agreement with results published in literature. The MCF uses a very small sample volume (in the order of 330 μL per meter length of material) and allows extremely rapid photolysis with a short contact time ranging from a fraction of seconds to few minutes. The novel microfluidic-based approach presented in this study is particularly useful for determining the photochemical behavior of highly priced pharmaceuticals, illicit drugs, metabolites and uncommon or regulated substances.