Behaviour of graphitized carbon black in the extraction of polar non-ionicnitrogen-containing pesticides. A checking of hypotheses

Graphitized Carbon Black (GCB) extractive cartridges are evaluated for on-l ine coupling with a C8 analytical column to determine eleven carbamates and one carboximide pesticide from spiked deionized water at the 1.2 mug/L lev el. Several experiments were carried out to ascertain whether GCB saturatio n, pesticide degradation on the surface, existence of by-pass channels, mob ility among the bulk cartridge, or strong retention on the surface interfer e with the determination of pesticides. Problems in on-line CGB elution are partially solved by modifying the aceto nitrile/water gradient to contain a front of 100% acetonitrile for a few se conds. Eluting the same GCB cartridges off-line with dichloromethane/methan ol gives recoveries higher than 77% for the selected pesticides.