Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2006
Publication Date: 10/1/2006
Citation: Cobb, J., Mattice, J., Senseman, S., Dumas, J., Mersie, W., Riley, M., Potter, T.L., Mueller, T., Watson, E. 2006. Pesticide Extraction Efficiency of Two Solid Phase Extraction Disk Types After Extraction and Shipping. Journal of Association of Official Analytical Chemists International. 89:903-912. Interpretive Summary: In water quality monitoring programs focused on pesticide residues shipment of samples to a testing laboratory for analysis is often required. Difficult logistical problems and high shipping costs are common when raw water samples are sent. In addition, studies have shown that some pesticides may degrade in water during shipment thereby compromising analytical results. Use of solid-phase-extraction cartridges (SPE) to concentrate and preserve pesticides from water after collection is an alternative. Typically cartridges weigh only few grams and can easily be sent to a laboratory by common carrier. Prior collaborative studies by our research group, the multi-state southern region project, S-1011, Water Quality Methodology for Crop Protection Chemicals, has shown that during shipping SPE devices may be subject to temperatures >38oC. This raised concerns about the stability of pesticides absorbed onto SPE devices since high temperatures can accelerate degradation reactions. In the current study, eight laboratories collaborated. Water was fortified with selected pesticides and extracted using commercially available SPE-extraction discs. Discs were stored for up to two weeks at temperatures spanning extremes likely to be observed in unprotected shipping containers. As temperature and storage time increased, recovery of some pesticides decreased substantially. Result demonstrate a need to avoid temperature extremes during shipment and long storage times of SPE discs after use in extracting water samples. Water quality monitoring programs will benefit when data are used to design quality assurance plans.
Technical Abstract: An interlaboratory study with 8 locations was conducted to assess the stability of pesticides on solid phase extraction disks (SPE) after incubation at various temperatures and time intervals. Deionized water fortified with selected pesticides was extracted using two types of SPE filtration disks (Empore™ C18 and Speedisk® C18XF) prior to incubation with fortified water at three temperatures (25, 40, 55°C) and two time intervals (4, 14 d). Deionized water was fortified with atrazine, carbofuran, and chlorpyrifos by all participating laboratories. In addition, some of the laboratories included two of the following pesticides: metolachlor, metribuzin, simazine, chlorothalonil, and malathion. Concurrent, fortified water samples were extracted with the incubated samples using each disk type at 4 and 14 d. Pesticides had equivalent or greater stability on at least one of the C18 disk types compared to storage in water. The lowest recovery of carbofuran (6%) and chlorpyrifos (7%) was obtained at 55°C after storage for 14 d in incubated water. At 55°C after 14 d, the lowest recovery for atrazine was 46% using Empore disks. Pesticide-specific losses occurred on the C18 disks in this study, underlining the importance of temperature and time interval when water is extracted at remote field locations and transported or shipped to a laboratory for elution and analysis.