COMPARISON OF VARIOUS SAMPLE HANDLING AND ANALYTICAL PROCEDURES FOR THE MONITORING OF PESTICIDES AND METABOLITES IN-GROUND WATERS

Various sample handling techniques such as liquid-liquid extraction of f-line and on-line, solid-phase extraction followed by either gas chro matography (GC) with electron-capture, flame phorometric or mass spect rometric detection, or liquid chromatography (LC) with diode array det ection were applied in the determination of a selected group of insect icides and fungicides in ground water samples at sub-mu g/l levels. An evaluation of the advantages and drawbacks in the application of the proposed methodologies for water monitoring studies is discussed. For the selected group of pesticides studied, off-line C-18 or polymeric c artridges followed by GC-MS using an ion trap analyzer have been revea led as the more powerful technique. But very polar compounds such as m ethamidophos or acephate have nor been recovered with this procedure. On the contrary, on-line C-18 LC-DAD offered a few drawbacks for the t race determination of a large group of pesticides as a consequence of many important interferences in the chromatographic traces. Other tech niques evaluated were LC-MS and GC-MS using a quadrupole analyzer, whi ch offered complementary information and were useful for a limited ran ge of analytes, An interlaboratory study was performed using all the m ethodologies evaluated in this work and the results obtained showed a good agreement between all the applied techniques. The various methodo logies were for a ground water pilot survey study in Almeria (Spain). Endosulfan was the most ubiquitous pesticide detected in this area. (C ) 1998 Elsevier Science B.V. All rights reserved.