Concentration and determination of trace amounts of chlorinated pesticides in aqueous samples

Summary

A method for the quantitative analysis of the organochloro-pesticides heptachlor, dieldrin, DDT and aldrin in water, using the HPLC technique of on-line trace enrichment, has been developed. A standard HPLC isocratic analytical system was employed the principle modification being the incorporation of a short pre-column across the sample loop connections of a Rheodyne 7125 valve to serve as the trace enrichment column. Pesticide recoveries of >95% were achieved at sample flow rate of 5–15 ml/min by employing stainless steel fittings throughout the system and with 5% methanol included in the pesticide sample reservoir. The pesticides were concentrated onto a 50 mm, 10 μm Spherisorb ODS column; analysis was performed on a 25 cm, 5 μm Spherisorb ODS column with methanol-water (75∶25) elution; detection was by UV absorption measurement at 220 mm and 0.64 AUFS.

Resolution achieved was >=1.16 and selectivity >=1.14. 100 ml aqueous samples allow ppb detection of the named pesticides in real samples. Total analysis time including concentration and chromatography was less than 30 minutes.