Determination of pesticides in drinking water using solid phase extraction GC/MS

In order to ensure the safety of drinking water supplies during the Athens Olympic Games, the monitoring of the drinking water in holding tanks at Olympic Venues was undertaken. Emphasis was given to the possible occurrence of chlorinated pesticides since these toxic organic compounds are easily accessible and completely miscible with water, making their detection impossible without analysis. Specifically, the pesticides alpha-BHC, beta-BHC, delta-BHC, lindane, heptachlor, aldrine, endosulfan 1, heptachlor epoxide, p-p' DDE, dieldrin, endosulfan II, p-p' DDD, endosulfan sulphate and methoxychlor were considered. A procedure was developed based on EPA method 525.2, 'Determination of organic compounds in drinking water by liquid solid extraction and capillary column gas chromatography/Mass Spectrometry' which is applicable to a wide range of organic compounds that are efficiently partitioned from a water sample onto a C18 organic phase chemically bonded to a solid matrix cartridge, and sufficiently volatile and thermally stable for gas chromatography. The organic compound analytes are extracted from a water sample by passing 1L of sample water through a cartridge containing a solid matrix with a chemically bonded C18 organic phase (solid phase extraction, SPE). The organic compounds are eluted from the cartridge with small quantities of ethyl acetate followed by methylene chloride. The method was altered in order to achieve maximum sample throughput. Thus the temperature program was modified in such a way as to allow efficient separation of the analytes of interest in the smallest amount of time. The elution process was altered in order to achieve better sample concentration. Elution of the solid phase extraction cartridge was performed by addition of 1ml ethyl acetate followed by 1ml methylene chloride. A very slow drop-by-drop elution rate was used. For a 1 L water sample, this gives a 500-fold concentration of the analytes. Recoveries for the analytes of interest were between 69-108%. Analysis of samples was performed immediately upon receipt. The pesticides of interest were successfully quantified with limits of detection ranging from 0.02-0.03 mu g/l. More than 2000 analyses were performed on samples from 15 Olympic game venues. The results were stored in a database and were presented in GIS map views.