SUPERCRITICAL FLUID EXTRACTION OF PESTICIDES AND PHTHALATE-ESTERS FOLLOWING SOLID-PHASE EXTRACTION FROM WATER

Solid phase extraction (SPE) was evaluated as a sample pretreatment method prior to supercritical fluid extraction (SFE) of pesticides or phthalate esters from spiked water samples. ODS, Florisil, Tenax GC and XAD4 resin were evaluated for their abilities to retain a mixture of 5 pesticides, and the use of supercritical CO2 as an elution solvent was investigated. SPE disks, impregnated with C-8 bonded phase silica were examined in both off- and on-line SFE. Using SPE disks prior to off-line SFE, supercritical CO2, and modified CO2 yielded recoveries comparable to liquid solvent extraction for five pesticides and four phthalate esters at the 100 ppb level. On-line SFE following disk SPE of chlorpyrifos at the 10 and 1 ppb levels yielded recoveries of 92 and 91%, respectively (%RSD = 7). The natures of supercritical solvents and their possible roles in the analysis of water samples is discussed.