Rapid determination of chlorinated pesticides in fish by freezing-lipid filtration, solid-phase extraction and gas chromatography-mass spectrometry.

An analytical method has been developed for measuring 24 chlorinated pesticides in fish tissue samples. Extraction of chlorinated pesticides was carried out by ultrasonication using an acetone-n-hexane (5:2, v/v) mixture. Most of the lipids in the extract were eliminated by freezing-lipid filtration, prior to solid-phase extraction (SPE) cleanup. During freezing-lipid filtration, about 90% of the lipids extracted from the fish samples were easily removed without any significant losses of chlorinated pesticides. For purification, SPE using Florisil was shown to be more effective than silica. Quantification was performed using gas chromatography-mass spectrometry in the selected ion monitoring mode. Spiking experiments were carried out to determine the recovery, precision, and limits of detection (LODs) of the method. The overall recovery was above 80% in the spiked fish tissue sample at 100 ng/g level. The detection limits for chlorinated pesticides were ranged from 0.5 to 5 ppb, except for endosulfan I and II which was 20 ppb. The newly developed method is demonstrated to give efficient recoveries and LODs for detecting chlorinated pesticides spiked into fish tissue with high lipid content.