|Wauchope, Robert - Don|
|Southwick Jr, Lloyd|
Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2000
Publication Date: 7/1/2000
Citation: Mueller, T.C., Senseman, S.A., Wauchope, R.D., Young, R.W., Southwick Jr, L.M., Riley, M.B., Moye, H.A., Dumas, J.A., Mersie, W., Mattice, J.D. 2000. Recovery of atrazine, bromacil, chlorpyrifos, and metolachlor from water samples after concentration on solid-phase extraction disks: interlaboratory study. Journal Of Association Of Official Analytical Chemists International. 83(6):1327-1333(2000).
Interpretive Summary: "Empore" disks are thin circular mats of teflon fiber coated with a wax- like material. When water is filtered through these disks many chemicals are absorbed out of the water. Large volumes of water (a liter or more) can be passed through the disks and the absorbed chemicals can then be released from the mats with a small volume (a few ml) of solvent, thus concentrating the chemicals several-hundred fold. Empore disks are a popular way of concentrating chemicals for analysis, such as pesticides that are often found at very low concentrations in water samples. In this project we determined how well the Empore disks work for four pesticides when 13 different laboratories in 10 states and Puerto Rico tried the technique on the same four pesticides. We also tried absorbing the chemicals in one location, mailing the disks to a distant location and analyzing the absorbed chemicals there. The results showed that the Empore etechnique is quite "robust", i.e., tends to work well in spite of the normal differences in technique between laboratories. The results are a strong confirmation of the Practical usefulness of these disks.
Technical Abstract: An inter-laboratory comparison was conducted to examine the utility of using C18 solid-phase extraction disks (Empore) to determine four pesticides in water samples. A common fortification and sample processing procedure were usd to minimize variation in initial concentrations and operator inconsistencies. Paired locations shipped fortified water samples sor Empore disks onto which the pesticides had been retained and then quantified the analytes using a variety of gas chromatographic methods. Average recoveries > 80% for atrazine, bromacil and metolachlor, and > 70% for chlorpyrifos. Detection of bromacil was unachievable at some locations due to chromatographic problems. Shipping samples between cooperating laboratories did not affect recovery of atrazine, chlorpyrifos, or metolachlor in either matrix. Recoveries tended to be higher where disks were shipped to cooperating labs compared with fortified water. Shipping disks eliminated many problems associated with the shipment of water samples. Recoveries were lower from fortified surface water samples compared to fortified deionized water samples for bromacil and metolachlor. This collaborative research demonstrated that water samples could be concentrated onto solid-phase extraction disks at one location and quantified using diverse analytical conditions at another location. Extraction efficiencies were comparable to or better than recoveries obtained from shipped water samples while eliminating the problems associated with the shipping of water samples.