DESICCATION EFFECTS ON STABILITY OF PESTICIDES STORED ON SOLID-PHASE EXTRACTION DISKS

摘要

Four desiccation methods were applied to pesticide-enriched solid-phase extraction disks (SPE) to determine whether enhanced stability would result when residual water was removed from SPE disks before storage, Pesticides were loaded onto 47-mm Empore C-18 disks by filtering 250 mL of deionized water fortified with 12 pesticides, After a 5-min vacuum and weight determination, the disks were further treated either by (1) freeze-drying, (2) vacuum desiccation with CaSO4, (3) storage in direct-contact with CaSO4, or (4) not desiccated, Disks were stored for 3, 10, or 30 days at either ambient or frozen temperatures, Desiccation treatments were equally effective at removing water from the disks; however, it was postulated that freeze-drying removed water faster than other desiccation treatments due to the strong vacuum (3.7 x 10(-6) MPa) and the higher recoveries of hydrolysis-susceptible analytes. Desiccation of disks resulted in lower recovery of trifluralin than from disks not desiccated, Frozen storage provided a more stable environment than ambient temperatures during storage for metribuzin, profenofos, and cyanazine but had little effect on the other compounds.