Analytica Chimica Acta, 283 (1993) 297-303 Elsevier Science Publishers B.V., Amsterdam 297 Solid-phase extraction of pesticide residues from ground water: comparison between extraction cartridges and extraction discs J. Beltran, F.J. Lopez and F. Hemandez Environmental and Natural Resources Laboratory, Department of Experimental Sciences, kume I University, P.O. Box 224, 12080 Casteltin &aid (Received 8th September 1992; revised manuscript received 9th February 1993) Abstract Gctadecyl (C,,) bonded porous silica sorbent cartridges and Empore membrane extraction discs were evaluated for the solid-phase extraction (SPE) of organochlorine (lindane, dicofol, chlorfenson and tetradifon) and organophos- phorus pesticides (dimethoate, fenitrothion and methidathion) from ground water. The SOO-mg Cts cartridges quantitatively adsorbed these pesticides, including the most polar (dimethoate), with recoveries ranging from 68 to 113% for a ground water sample spiked at the 0.1 pg I-’ level. SPE with 500-mg C,, Empore discs also quantitatively adsorbed the pesticides with recoveries between 73 and 115% for the 0.1 pg I-’ level, but only after eluting with 15 ml of ethyl acetate compared with 4 ml using cartridges and a longer analysis time per sample. After elution with ethyl acetate, the extract was concentrated to an appropriate volume, between 100 and 500 ~1, under a gentle stream of nitrogen. Detection limits were lower than 0.1 pg l-‘, which is currently the mazimum level allowed by the EEC for pesticide residues in drinking water. Determination was effected by capillary gas chromatography using electron-capture and nitrogen-phosphorus detectors. Keywords: Gas chromatography; Extraction; Pesticides; Waters One of the most important environmental con- cerns is pesticide residue levels in water, mainly in ground water in predominantly agricultural areas, and their movement in the ecosystem. This has led to the development of multi-residue methods for the determination of pesticides in environmental samples. Unfortunately, classical analytical procedures based on solvent partition- ing in separation funnels are time consuming and require large volumes of costly and toxic solvents. The solid-phase extraction (SPE) system using bonded silica sorbents applied to the extraction of pesticides from water offers the advantages of Comqondence to: F. Hemandez, Environmental and Natural Resources Laboratory, Department of Experimental Sciences, Jaume I University, P.O. Box 224, 12080 Castellon (Spain). a shorter analysis time, lower cost and the con- sumption of very low volumes of organic solvents. Organochlorine and organophosphorus pesti- cides have been determined in water samples using SPE using a variety of sorbents such as C,, [l-6], Cs [7-91 and Amberlite XAD [lo-131. Em- pore membrane extraction discs can be used as an alternative to cartridge SPE. These can be used in the off-line mode with a filtration appara- tus [14] and in the on-line mode using a mem- brane holder [15,16]. The pesticides studied in this work included some of the most commonly applied compounds in this area of Spain. They include the organo- phosphorus (OP) pesticides dimethoate, feni- trothion and methidathion and the organo- chlorine (OC) pesticides lindane, dicofol, chlor- 0003-2670/93/$06.00 0 1993 - Elsevier Science Publishers B.V. All rights reserved