SOLID-PHASE MICROEXTRACTION AND GAS-CHROMATOGRAPHY WITH MASS-SPECTROMETRIC DETECTION FOR THE DETERMINATION OF PESTICIDES IN AQUEOUS SAMPLES

Solid-phase microextraction (SPME) is a fast, alternative method for e xtracting organochlorine, triazine and thiocarbamate pesticides. An 85 -mu m polyacrylate fiber was used to extract the analytes directly fro m aqueous samples and then thermal desorption was carried out in the h ot injector of a gas chromatograph-mass spectrometer. To enhance the s ensitivity of SPME, the temperature and the length of the extraction a nd desorption steps and the pH and salt concentration of the sample we re optimized. The linearity of most of pesticides for real samples was found to be between 0.07 and 30 mu g 1(-1) when GC-MS under full-scan acquisition was used and between 0.005 and 10 mu g 1(-1) when selecte d-ion monitoring (SIM) acquisition was used. Limits of detection at th e sub mu g 1(-1) level were achieved with GC and MS under the full-sca n acquisition mode and at the ng 1(-1) level for MS under SIM acquisit ion. The repeatability of the method for tap water spiked at a level o f 0.5 mu g,a 1(-1) (n=5) was below 25% (R.S.D.). (C) 1998 Elsevier Sci ence B.V.