Influence of Salinity and Dissolved Humic Acids on Pesticides Extraction from Water Using Solid-Phase Extraction Disks

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Abstract
The influence of water salinity and dissolved organic matter (DOM) on pesticide extraction recoveries using solid phase extraction disks was investigated. Eleven selected pesticides, belonging to different chemical groups were spiked at 1–5 μg/L in 500 ml distilled water containing sodium chlorine at 0, 5, 10, 15, 20, 25, 30 and 35 ‰ or humic acids at either 0, 1, 5, 10, 25, 50 and 100 mg/L dissolved organic carbon (DOC). Samples were prefiltered and their extraction was done by using C18 Empore solid phase extraction disks and filter aid glass beads. The pesticides eluted from the disks were analysed by gas chromatography with flame thermoionic detector (FTD) and mass selected detector (MSD) in the selected ion monitoring (SIM) mode. Higher recoveries of most pesticides were obtained as the water salinity increased from 0 to 35 ‰. Concentrations of DOC in humic acid had less effect on extraction efficiency, which was probably due to greater nonpolar interactions of pesticides to the charge-neutralized humic acid polymer.