On-line in-syringe sugaring-out liquid-liquid extraction coupled with HPLC-MS/MS for the determination of pesticides in fruit and berry juices

A fully automated method for the determination of pesticides (malathion, diazinon, imidacloprid and triadimefon) in fruit and berry juices has been developed. In the current study, the on-line in-syringe sugaring-out liquid-liquid extraction was successfully combined with a HPLC-MS/MS system for the first time. The procedure assumes the liquid-liquid extraction of analytes in water-miscible organic solvent acetonitrile followed by phase separation using glucose as sugaring-out reagent. After the phase separation in a syringe of a flow system, the extract containing pesticides was injected into the HPLC-MS/MS system. The proposed automated sample preparation procedure is rapid, simple, relatively inexpensive, and allows to avoid shortcomings of conventional liquid-liquid extraction, such as necessity to use nonpolar organic solvents, which are not always suitable for the HPLC-MS/MS detection. The conditions of pesticides' extraction such as ratio of acetonitrile/water, type and concentration of sugaring-out reagent, volume of sample and effect of pH have been studied and optimized. Under optimal experimental conditions the linear detection ranges were found to be 10(-2)-10 mg L-1 for malathion and triadimefon, 10(-3)-10 mg L-1 for diazinon, and 10(-1)-10 mg L-1 for imidacloprid. The LODs, calculated from a blank test, based on 3 sigma, found to be 3.10(-3) mg L-1 for malathion and triadimefon, 3.10(-4) mg L-1 for diazinon and 3.10(-2) mg L-1 for imidacloprid. The application of the method has been demonstrated in the determination of these four pesticides in commercial samples of five fruit and berry juices. As an outcome, the analytical results agreed fairly well with the results obtained by a reference GCFID method.