Enhancing reactive species generation upon photo-activation of CdTe quantum dots for the chemiluminometric determination of unreacted reagent in UV/S2O82−S2O82− drug degradation process

• A multipumping flow process was proposed to monitor the persulfate in aqueous system.
• A photochemical degradation of drugs is proposed based on QDs properties.
• The persulfate contribution on drugs oxidation by S2O82−S2O82−/UV system was evaluated.
• Persulfate homolysis sulfate radicals were promoted by QDs.
• Synergistic effect of UV/QDs and S2O82−S2O82− ions for free radicals production was attested.

A new chemiluminescence (CL) flow method for persulfate determination was developed based on luminol oxidation by in-line generated radicals. Reactive oxygen species (ROS) generated by CdTe quantum dots (QDs) under a low energetic radiation (visible light emitted by LEDs) promoted the decomposition of persulfate ion (S2O82−S2O82−) into sulfate radical (SO4∙−), leading to subsequent radical chain reactions that yield the emission of light. Due to the inherent radical short lifetimes and the transient behavior of CL phenomena an automated multi-pumping flow system (MPFS) was proposed to improve sample manipulation and reaction zone implementation ensuring reproducible analysis time and high sampling rate. The developed approach allowed up to 60 determinations per hour and determine S2O82−S2O82− concentrations between 0.1 and 1 mmol with good linearity (R=0.9999). The method has shown good repeatability with relative standard deviations below 2.5% (n=3) for different persulfate concentrations (0.1 and 0.625 mmol L−1). Limits of detection (3σ) and quantification (10σ) were 2.7 and 9.1 µmol L−1, respectively. The MPFS system was applied to persulfate determination in bench scale UV/S2O82−S2O82− drug degradation processes of model samples showing good versatility and providing real time information on the persulfate consumption in photo-chemical degradation methodologies.

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