COMPARISON OF SOLID-PHASE EXTRACTION TECHNIQUES FOR HERBICIDES

Solid phase extraction (SPE) procedures were used to determine the rec overies of herbicides typically used in containerized ornamental plant production from water samples. Recoveries from Cls cartridges and dis ks were compared for each of 12 herbicides with variations in elution solvent and volume of elution solvent tested. Recoveries for nine of t he herbicides from the cartridges and disks using acetone as an elutio n solvent were not affected by SPE matrix. Fluazifop recovery was grea ter with the disks, while napropamide and oxadiazon recoveries were gr eater with cartridges. Both cartridges and disks yielded low recoverie s (23 to 47%) of benefin and prodiamine. Changing the elution solvent from acetone to acetonitrile resulted in 10% improvement for the recov ery of benefin and a three- to four-fold increase in recovery of prodi amine. Acetonitrile decreased recoveries of napropamide, oryzalin, oxa diazon, oxyfluorfen, and pendimethalin from cartridges. For the disks, oxyfluorfen, prodiamine, and trifluralin had increased recovery, whil e fluazifop, oxadiazon, and simazine had decreased recovery,vith aceto nitrile as the elution solvent. Increasing the amount of acetone eluti ng solvent increased the recovery of prodiamine and oxyfluorfen while decreasing the recovery of fluazifop, pendimethalin, simazine, and tri fluralin. Binding capacities of oryzalin on cartridges and disks avera ged 13.2 and 7.8 mg, respectively. The advantage of the disk lies in t he greater volume of water that can be processed, while the higher cos t and greater variability are disadvantages. Cartridge extraction yiel ded good recoveries with lower standard deviations, and used less orga nic solvent. Selection of an SPE extraction method depends upon the he rbicides under evaluation, expected levels, and the water volume being processed. Both SPE techniques offer advantages over traditional liqu id-liquid extraction methods such as reduced requirements for organic solvent and sample preparation.