EPA Method 522
A water sample that has been dechlorinated and preserved with a microbial inhibitor is fortified with the isotopically labeled SUR, 1,4-dioxane-d8. The sample is extracted by one of two SPE options. In option 1, a 500-mL sample is passed through an SPE cartridge containing 2 g of coconut charcoal to extract the method analyte and SUR. In option 2, a 100-mL sample is extracted on a Waters AC-2 Sep-Pak or Supelco Supelclean ENVI-Carb Plus cartridge. In either option, the compounds are eluted from the solid phase with a small amount of dichloromethane (DCM), approximately 9 mL or 1.5 mL, respectively.
The extract volume is adjusted, and the IS, tetrahydrofuran-d8 (THF-d8), is added. Finally, the extract is dried with anhydrous sodium sulfate. Analysis of the extract is performed by GC/MS. The data provided in this method were collected using splitless injection with a high-resolution fused silica capillary GC column that was interfaced to an MS operated in the SIM mode.
The analyte, SUR and IS are separated and identified by comparing the acquired mass spectra and retention times to reference spectra and retention times for calibration standards acquired under identical GC/MS conditions. The concentration of the analyte is determined by comparison to its response in calibration standards relative to the IS. Although the performance data presented in Section 17 of this method were obtained in the SIM mode for maximum method sensitivity, the sample extract analysis may also be performed in full scan mode if the sensitivity achieved meets the data user’s requirements.
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