Reference method for PCDDs and PCDFs in pulp and paper mill effluents: section 8


Section 8: Quality Assurance Summary

Required quality assurance elements of this method are summarized as follows:

  1. Before any effluent samples are processed, all pre-cleaned glassware, including Soxhlet apparatus, concentrators, columns, flasks, and vials, are rinsed with dichloromethane and hexane. Rinses are combined and processed in the same manner as test samples. Contamination levels of individual 2,3,7,8-substituted tetra, penta, hexa, hepta and octa CDD/CDF congeners in glassware proof rinses must not exceed 5, 10, 10, 15 and 50 pg per sample, respectively.
  2. Before any effluent samples are processed, laboratory capability must be demonstrated by conducting triplicate analyses of matrix blanks (purified water) spiked with native and labelled PCDD/PCDF standards. Criteria for accuracy and surrogate recoveries described in Subsection 5.2 must be met.
  3. Before extraction, each sample is spiked with a mixture of isotopically-labelled surrogates to assess the degree of analyte loss during sample workup. If the recovery of any surrogate is outside the range of 40 to 130% for TCDD and TCDF, and 30 to 130% for penta, hexa, hepta and octa CDDs/CDFs, the sample must be re-processed and re-analyzed.
  4. Known concentrations of 13C12-1,2,3,4-TCDD and 13C12-1,2,3,7,8,9-H6CDD must be added to each sample extract immediately before GC/MS analysis. These two compounds serve as retention time references for labelled surrogates and as the basis for calculation of surrogate recoveries.
  5. A method blank sample, consisting of 1 L of high purity water spiked with surrogates, is processed with each batch of up to 10 test samples. Acceptance limits for 2,3,7,8-substituted dioxin and furan congener presence in method blank samples are: 5 pg for TCDD and TCDF; 10 pg for penta and hexa CDD/CDF; 15 pg for hepta CDD/CDF; 50 pg for OCDD/OCDF. A compliance sample result for a 2,3,7,8-substituted congener must be flagged with a "C" if the same congener was present in the corresponding method blank at a level exceeding the applicable acceptance limit.
  6. Hard copied verification of MS resolution at 10 000 or better is required before and after each series of injections related to the application of this method.
  7. A Window Defining Mixture containing the first and last eluting isomer within each homologous group of PCDDs/PCDFs must be used to correctly define retention time windows for selected ion monitoring of individual homologues. This analysis must be repeated daily (see Subsection 6.2 and Subsection 6.3.
  8. Acceptable chromatographic separation between 2,3,7,8-TCDD and its closest neighbouring isomers must be confirmed daily. If analysis for 2,3,7,8-TCDF on a second column is required, acceptable chromatographic separation between this isomer and its closest neighbouring isomers must also be demonstrated. (See Subsections 6.3.)
  9. Before sample analysis, calibration curves are constructed to verify linearity of MS response for all homologues over the concentration range of 0.25 to 100 pg/μL for native PCDDs/PCDF (see Subsection 6.6).
  10. The established calibration must be verified by analyzing the calibration verification standard (CS3) at least once during every 12-hour period in which sample analysis occurs. Using four-point average RRFs obtained from initial calibration runs, the calculated concentrations of both 2,3,7,8-TCDD and 2,3,7,8-TCDF must be within 15% of their actual values. The calculated concentrations of all other native analytes must bewithin 20% of their respective true concentrations. The calculated recovery of each surrogate compound must be within the range of 75 to 125%. Remedial action is required whenever any native or surrogate compound fails this verification test (see Subsections 6.4 and Subsection 6.6).
  11. Gas chromatograph/mass spectrometer (GC/MS) detection limits must be assessed by analyzing the lowest concentration (CS1) standard solution. This analysis must be repeated daily.
  12. As a check on accuracy, NIST (formerly NBS) Reference Material 1614 (2,3,7,8-TCDD in solution) is periodically analyzed as a sample. This aspect of the QA program should be enhanced by the use of other reference materials, as they become available.
  13. Reported sample results must be fully documented. All QA/QC documentation and raw GC/MS data, must be available for auditing (see Section 7).
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