Separation of a binary mixture of pesticides in fruits using a flow-through optosensor

A flow-through optosensor is here proposed for the determination of mixtures of two widely used pesticides, carbendazim and o-phenylphenol, in fruits. The pesticides are separated on-line using an additional amount of solid support, C18 silica gel, in the flow-through cell. The resolution is performed due to the different retention/desorption kinetics of the analytes when interacting with the C18 microbeads. Therefore, both separation and determination are integrated in the same cell, considerably simplifying the system. In addition, the use of Sequential Injection Analysis provides a high degree of automation and minimum wastes generation. After the analytes are separated, their native fluorescence is measured, obtaining linearity in the 2.0–30 and 1.1–20 mg kg−1 ranges for carbendazim and o-phenylphenol. The detection limits are 0.60 and 0.33 mg kg−1 for carbendazim and o-phenylphenol respectively. The proposed method fulfills the maximum residue limits (MRLs) established in Europe and USA for these pesticides in cherries, pineapple, and mango: 5–10 mg kg−1. In order to demonstrate the suitability of the method, several samples have been analyzed and the obtained results compared with a chromatographic method.