Determination of Chlorpyrifos by a Multicommutated Photochemically Induced Fluorescence Optosensor

摘要

We propose a multicommutated flow-through optosensor for the quantitation of the organophosphate pesticide chlorpyrifos in dried chili peppers. We used photochemically induced fluorescence detection to overcome the negligible native fluorescence of the target pesticide. Firstly, the photodegradation of chlorpyrifos was performed online with an ultraviolet lamp. Then, the fluorescent photoproduct was retained on a solid support (Sephadex QAE A-25) inside the flow-cell in order to record the analytical signal. The online photodegradation and preconcentration of the photoproduct on the solid support were critical for the automation, speed, and high sensitivity obtained. A QuEChERS procedure was selected for sample treatment, obtaining recovery yields close to 100%. The method proposed presents a quantitation limit of 18 mg kg(-1) in real samples, hence fulfilling the maximum residue limit of Codex Alimentarius, 20 mg kg(-1). Therefore, this approach offers a novel method for screening purposes in the agricultural and food industries.