MICROEXTRACTION PROCEDURES COMBINED WITH LARGE-VOLUME INJECTION IN CAPILLARY GAS-CHROMATOGRAPHY FOR THE DETERMINATION OF PESTICIDE-RESIDUESIN ENVIRONMENTAL AQUEOUS SAMPLES

Liquid-liquid microextraction and solid-phase extraction procedures co mbined with large volume on-column injection (100-150 mu l) in capilla ry gas chromatography with nitrogen phosphorus detector have been appl ied to the determination of six triazine herbicides (atrazine, simazin e, terbutylazine, terbumeton, metribuzin and terbutryn) and two transf ormation products (deethyl and deisopropyl atrazine) in water samples. A simple and fast off-line liquid-liquid microextraction procedure (5 mi water/1 mi methyl tert butyl ether) was applied to surface water s amples spiked at 0.5 mu g l(-1) level with good recoveries (> 90%) and repeatability (better than 9%) giving detection limits < 0.1 mu g l(- 1). The application of a solid-phase extraction procedure (10-50 ml of water samples passed through 200 mg C-18 cartridges) allowed the quan titative recovery of all pesticides studied with coefficients of varia tion lower than 11%. Limits of detection for 50 ml sample volume range d from 10 to 40 ng l(-1). Surface water samples have been analyzed usi ng C-18 SPE (10 mi of water sample) combined with large volume injecti on (150 mu l) and the results compared with those obtained with conven tional LLE (500 mi of water sample extracted with 2 x 50 ml dichlorome thane), showing good match between them. (C) 1997 Elsevier Science B.V .