Pesticide residue analysis by off-line SPE and on-line reversed-phase LC-GC using the through oven-transfer adsorption/desorption interface

A new method to determine pesticide residue in water is presented. The desc ribed method includes using off-line solid-phase exb;action (SPE) and on-li ne reversed-phase liquid chromatography-gas chromatography (RPLC-GC). An in terface, based on a modified programmed temperature vaporizer (PTV) injecto r, packed with a suitable trapping material, is used for on-line RPLC-GC. T he changes made in the PTV injector affect the pneumatic system, sample int roduction, and solvent elimination. The new interface is easily capable of automation. Methanol/water (70/30) is used as the eluent in the LC presepar ation step. The LC column now during elution is different from the now duri ng the transfer step. The transferred volumes range from 500 to 1400 mu L ( volume of the fractions of interest). Solvent elimination is almost 100% be fore the sample reaches the GC column. The described system does not show a ny variation of the peak retention times. The detection limit for real samp les ranges from 0.04 to 1.5 ng/L, using NP detection.