Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Abstract only
Publication Acceptance Date: 5/31/2002
Publication Date: 6/1/2002
Citation: MERSIE, W., CLEGG, C.M., WAUCHOPE, R.D., DUMAS, J., LEIDY, R., REILEY, M., YOUNG, R., MATTICE, J., MUELLER, T., SENSEMAN, S. INTERLABORATORY COMPARISON OF PESTICIDE RECOVERY FROM WATER USING SOLID-PHASE EXTRACTION DISKS. JOURNAL OF ASSOCIATION OF OFFICIAL ANALYTICAL CHEMISTS INTERNATIONAL 85:1324-1330. 2002. Interpretive Summary: The Hatch Act Southern Region Technical Committee S-271, "Pesticides in the Agricultural Environment" is a cooperative research project which brings together a group of Southeastern pesticide analytical chemists and environmental scientists to discuss methodology, keep each other up to date on pesticide issues, and develop interlaboratory projects to develop analytical techniques applicable to a wide variety of pesticides. This paper is one of two resulting from the preparation of standard very-low-concentration water solutions of pesticides and sharing them with all the laboratories to determine how reproducible our analytical methods are. We all used the "solid phase extraction" method, a widely-used method but one that has received little interlaboratory study. Results were mixed.
Technical Abstract: An interlaboratory collaborative study was conducted to assess the suitability of C18 solid-phase extraction disks to retain and ship different pesticides from water samples. Surface and deionized water samples were fortified with various pesticides and were extracted using C18 disks. Pesticides were eluted from disks and analyzed in-house or disks were sent to another laboratory where they were eluted and analyzed. Along disks, a portion of the standard pesticide mix in methanol was also shipped to be used for fortification, extraction, and analysis. Recoveries of pesticides from in-house eluted disks were compared with those eluted from shipped disks. The highest recovery from deionized or surface water using shipped disks was obtained for cyanazine (>97%), followed by metalaxyl (>96%), and atrazine (>92%). But the retention and transportability of some pesticides were affected by the type of water used for fortification. Less than 40% of the bifenthrin, chlorpyrifos and chlorothalonil fortified in surface water were recovered from shipped disks while from deionized water the recoveries were greater than 70%. From in-house eluted disks, bifenthrin was recovered at 118%, chlorpyrifos at 105% and chlorothalonil at 71% indicating the poor recovery from surface water is loss during shipping rather than low retention by the C18 disks. For the majority of the 13 pesticides tested, there was no difference in recovery between in-house extracted and shipped disks indicating the suitability of disks to concentrate and transport pesticides.