Multicommutated Flow System for the Determination of Glyphosate Based on Its Quenching Effect on CdTe-Quantum Dots Fluorescence

Glyphosate is the most widely used herbicide at the moment. It presents a broad spectrum of action, hence its use for many different crops. Regulatory agencies have constantly mentioned the low hazard potential to mammals. However, the International Agency for Research on Cancer concluded in 2015 that glyphosate is probably carcinogenic to humans. For this reason, it is important to develop reliable analytical methods to study the fate and levels of glyphosate in environmental samples. In this work, we propose a multicommutated flow analysis method for the determination of glyphosate, based on the quenching effect produced by this herbicide on the fluorescence of CdTe quantum dots (lambda(exc)/lambda(em) 400/548 nm/nm). The proposed analytical method presents detection and quantitation limits of 0.5 and 1.7 mu g mL(-1), respectively. A sample throughput of 30 samples per hour was achieved using a 2.5 mL min(-1) flow rate. Interference studies were carried out to assess the selectivity of the method, observing no interference from other common pesticides. Finally, we carried out recovery experiments in water and cereal samples (amaranth, barley, oat, and quinoa). We obtained recovery yields between 92 and 108% in all the analyzed samples. HPLC-MS/MS was used as reference method to assess the accuracy of the proposed methodology.