A new sample clean-up procedure, based on ion-pairing on RP-SPE cartridges, for the determination of ionizable pesticides

Abstract

Residues of ionizable pesticides in lemon extracts were isolated by a new solid-phase extraction method on reverse-phase cartridges. Cartridges were preconditioned with zwittergents such as cetyltrimethylammonium bromide for anionic pesticides and sodium dodecyl sulphate for cationic pesticides. Zwittergents and opposite charged analytes produce ion pairs that are stronger retained on the cartridge bed than the native analytes. Following washings of the cartridge, with an eluent of suitable concentration in organic solvent, resulted in interference removal. Finally, pesticides were eluted with acetonitrile. Based on the aforementioned procedure, two analytical methods were developed for the determination of acidic (2,4,5-trichlorophenoxyacetic acid, dichlorprop, and dinoseb) and basic (carbendazim and thiabendazole) pesticide residues in lemons. The analytes were separated on a reverse-phase C₁₈ HPLC column and detected by UV.

Keywords:

• Solid-phase extraction (SPE)
• Ion-pair reagent
• High-performance liquid chromatography (HPLC)
• Pesticides
• Sodium dodecyl sulphate (SDS)
• Cetyltrimethylammonium bromide (Ctab)

Acknowledgements

We thank the European Social Fund (ESF), Operational Programme for Educational and Vocational Training II (EPEAEK II), and particularly the Programme HERAKLEITOS, for funding the above work.