Evaluation of parameters in solid-phase microextraction process

Solid-phase microextraction has been used successfully to determine organic pollutants in environmental samples. To date, absorption and desorption co nditions in SPME have been widely studied. This paper evaluates the effect of other parameters, such as storage time and the addition of an internal s tandard to the sample, for a group of five pesticides (Irgarol 1051, Atrazi ne, Lindane, Dieldrin and Molinate) in aqueous samples. Adding an internal standard to the sample does not improve the repeatability and the reproduci bility of the results. A storage time of 900 minutes does not significantly decrease the response of any of the pesticides studied except Irgarol 1051 . Storage times of < 15 min were needed to determine this pesticide without a decrease in the response.