Conditions for solid-phase extraction of agricultural chemicals in waters by using n-octanol-water partition coefficients

The sorption and desorption behaviour of 25 aromatic compounds and 20 agricultural chemicals, in solid-phase extraction (SPE), were investigated in relation to the n-octanol-water partition coefficients (PoW) of different chemicals using various adsorbents in Sep-Pak cartridges. Recoveries were related to PoW, those with high PoW values being easily sorbed but difficult to elute. The extent of elution was improved by the addition of methanol to the sample solution. Optimal SPE conditions for enrichment and separation could be selected approximately using the PoW as a key parameter. Some applications were tested with good results. The influences of humic acids and surfactants on recoveries were also studied. It was suggested that SPE conditions for the various commercially available sorbents could be chosen by reference to the SPE behaviour of benzoates.