EPA Method 1625

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EPA Method 1625:
Semivolatiles - Base/Neutrals, Acid Extractable, GC/MS. Official Name: Semivolatile Organic Compounds by Isotope Dilution GCMS

Stable isotopically labeled analogs of the compounds of interest are added to a 1-L wastewater sample. The sample is extracted at pH 12-13, then at pH

This method is designed to determine the semivolatile toxic organic pollutants associated with the 1976 Consent Decree and additional compounds amenable to extraction and analysis by capillary column gas chromatography-mass spectrometry (GC/MS).

EPA Method Guidance CD-ROM (includes MCAWW Methods, and most current EPA Methods)

(A) Artifacts: Solvents, reagents, glassware, and other sample processing hardware may yield artifacts and/or elevated baselines causing misinterpretation of chromatograms and spectra. Use of pure or purified reagents and solvent rinsed and baked glassware can minimize potential for artifacts.(2) Matrix: Interferences coextracted from samples will vary considerably from source to source, depending on the diversity of the industrial complex or municipality being sampled.

QC Requirements:
The minimum QC requirements consist of an initial demonstration of laboratory capability, analysis of samples spiked with labeled compounds to evaluate data quality, and analysis of standards and blanks as tests of continued performance. Laboratory performance is compared against established criteria.

Maximum Holding Time:
7 days (sample prior to extraction); 40 days (extract)



Varies with analyte.

Summarized data results are based on quantification by isotope dilution. Precision and accuracy data were obtained from "Interlaboratory Validation of U.S. Environmental Protection Agency Method 1625A" (July 1984). Study data were collected for samples analyzed at 11-13 laboratories, depending on compounds. Approximately twenty-three percent of laboratories could not quantify or detect compounds by isotope dilution, so these laboratories were excluded from method summaries (the need for these exclusions was primarily based on lack of experience with the method at the time of the 1984 study).

(1) The values given are the minimum level at which the entire GC/MS system must give recognizable mass spectra (background corrected) and acceptable calibration points.(2) The values given refer to one of three techniques for each compound: internal standard quantification, labeled compound quantification, and isotope dilution quantification. Consult Table 3 of the method for information on specific compounds.

Revision Number:
40 CFR Part 136, Appendix A (Current Edition)