Interlaboratory Comparison of Extraction Efficiency of Pesticides from Surface and Laboratory Water Using Solid-Phase Extraction Disks

• Published in: Journal of agricultural and food chemistry 2003-06, Vol.51 (13), p.3748-3752
• Main Authors: Senseman, Scott A, Mueller, Thomas C, Riley, Melissa B, Wauchope, R. Don, Clegg, Chris, Young, Roddy W, Southwick, Lloyd M, Moye, H. Anson, Dumas, Jose A, Mersie, Wondi, Mattice, John D, Leidy, Ross B
• Format: Article
• Language: English
• Subjects: Acetamides - analysis; atrazine; Atrazine - analysis; Biological and medical sciences; bromacil; Bromouracil - analogs & derivatives; Bromouracil - analysis; chlorpyrifos; Chlorpyrifos - analysis; Chromatography, Gas; Filtration - instrumentation; Fundamental and applied biological sciences. Psychology; Glass; Laboratories; metolachlor; Pesticides - analysis; Quality Control; quantitative analysis; shipping; solid phase extraction; Water - analysis
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf026040z

A continuation of an earlier interlaboratory comparison was conducted (1) to assess solid-phase extraction (SPE) using Empore disks to extract atrazine, bromacil, metolachlor, and chlorpyrifos from various water sources accompanied by different sample shipping and quantitative techniques and (2) to compare quantitative results of individual laboratories with results of one common laboratory. Three replicates of a composite surface water (SW) sample were fortified with the analytes along with three replicates of deionized water (DW). A nonfortified DW sample and a nonfortified SW sample were also extracted. All samples were extracted using Empore C18 disks. After extraction, part of the samples were eluted and analyzed in-house. Duplicate samples were evaporated in a 2-mL vial, shipped dry to a central laboratory (SDC), redissolved, and analyzed. Overall, samples analyzed in-house had higher recoveries than SDC samples. Laboratory × analysis type and laboratory × water source interactions were significant for all four compounds. Seven laboratories participated in this interlaboratory comparison program. No differences in atrazine recoveries were observed from in-house samples analyzed by laboratories A, B, D, and G compared with the recovery of SDC samples. In-house atrazine recoveries from laboratories C and F were higher when compared with recovery from SDC samples. However, laboratory E had lower recoveries from in-house samples compared with SDC samples. For each laboratory, lower recoveries were observed for chlorpyrifos from the SDC samples compared with samples analyzed in-house. Bromacil recovery was 75%. Three laboratories showed no differences in metolachlor recovery; two laboratories had higher recoveries for samples analyzed in-house, and two other laboratories showed higher metolachlor recovery for SDC samples. Laboratory G had a higher recovery in SW for all four compounds compared with DW. Other laboratories that had significant differences in pesticide recovery between the two water sources showed higher recovery in DW than in the SW regardless of the compound. In comparison to earlier work, recovery of these compounds using SPE disks as a temporary storage matrix may be more effective than shipping dried samples in a vial. Problems with analytes such as chlorpyrifos are unavoidable, and it should not be assumed that an extraction pro