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

Abstract

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 C(18) 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 x analysis type and laboratory x 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 <65% at two of the seven laboratories in the study. Bromacil recoveries for the remaining laboratories were >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 procedure using SPE disks will be adequate for all compounds and transferrable across all chromatographic conditions.

Prokaryotic Gene Profiling Assays to Detect Sediment Toxicity: Evaluating the Ecotoxicological Relevance of a Cell-Based Assay

“…Both water column and pore water samples were extracted by vacuum filtration over 47 mm Empore C18 and SDB−RPS membranes (3M, Belgium), according to the guidelines of the manufacturer ( − ). The Empore C18 membranes consist of bonded silica with a 60 Å pore size to which octadecyl groups are attached, giving the membrane a strongly nonpolar affinity.…”

Atrazine residues in flooded and nonflooded soil and effects on soybean

“…More widely, Knox County grows <270 ha of corn annually (Bowing and Smith 2019), all of which lies downriver from this site. The most recent sampling of the same area of the river showed no atrazine to be present, even when multiple analytical laboratories separately examined the water from this same location (Senseman et al 2003). Based on these factors, these authors strongly assert that the water used in the flooding regimen contained no atrazine.…”

Pesticide Extraction Efficiency of Two Solid Phase Disk Types after Shipping

“…Studies were conducted to determine if sample integrity was maintained when pesticides sorbed to the Empore SPE disks were shipped to an analytical laboratory. Results showed that minimal recovery losses were observed during the shipment of disks ( − ). Observed losses were pesticide specific when using this two-stage analytical procedure ().…”