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IS TCLP ALWAYS REQUIRED?
Not if a total metals analysis demonstrates that individual metal levels are low enough:
- SCOPE AND APPLICATION Section 1.2 indicates that "If a total analysis of the waste demonstrates that individual analytes are not present in the waste, or that they are in such low concentrations that the appropriate regulatory levels could not possibly be exceeded, the TCLP need not be run."
- The "total analysis" refers to Method 3050A. In performing this analysis, any individual metal found at levels less than or equal to 20 times the TCLP limits would not need TCLP analysis performed. This is particularly pertinent with a metal like Ag, since a special preparation may be necessary (Method 7760A).
IS NITRIC ACID DIGESTION ALWAYS REQUIRED FOR TCLP?
Not if a precipitate is observed when nitric acid is added:
- SAMPLE COLLECTION, PRESERVATION, AND HANDLING Section 6.6 indicates that "Extracts or portions of extracts for metallic analyte determinations must be acidified with nitric acid to a pH <2, unless precipitation occurs..." (emphasis added). This is confirmed in PROCEDURE Section 7.2.14.
IF THE NITRIC ACID DIGESTION IS NOT USED, WHAT ABOUT 40CFR 266.112 RESIDUES COMPLIANCE?
Unfortunately, while PROCEDURE Section 7.2.14 allows for omission of the nitric acid digestion "if precipitation is observed" and/or "except in those instances where digestion causes loss of metallic analytes", it also goes on to say, "However, data on undigested extracts alone cannot be used to demonstrate that the waste is not hazardous."
SO WHAT ABOUT MAINTENANCE OF BEVILL STATUS?
If no precipitate is observed during the sample preparation, you would proceed with the nitric acid digestion through to completion of Method 1311. You can omit Method 7760A for silver if a total metal analysis demonstrates low enough concentrations, according to SCOPE AND APPLICATION Section 1.2.
ARE THERE OTHER PERTINENT TCLP PROCEDURAL ISSUES?
It is of interest to note that Antimony is not listed in Method 3050A for total metal analysis. Neither is Antimony mentioned in Method 3010, ACID DIGESTION OF AQUEOUS SAMPLES AND EXTRACTS FOR TOTAL METALS FOR ANALYSIS BY FLAA OR ICP SPECTROSCOPY. The wavelength and estimated instrumental detection limit for Antimony is listed in Method 6010A, INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY; however interferences from Al, Cr, Fe, Tl & V are indicated.
The following text has been developed to go with the flow chart provided (See Figure 1) to help facilitate analytical decisions regarding TCLP metal leachate sample preparation and test methods:
- First Step (optional, top left box) - perform a total metal analysis (Method 3050/7471) to determine individual metal concentrations
- Second Step (next box below top left box) - determine if any metal concentration is less than or equal to 20 times the corresponding TCLP limit as found in 40CFR 266 Appendix VII and listed below:
- Third Step
* any metal concentration that is less than or equal to 20 times the TCLP limit passes the TCLP test and no further analysis is necessary for that metal (bottom left box)
* or remaining metals, perform Method 1311 TCLP extraction procedure (top middle box)
- fourth step (middle flow chart choices) - perform appropriate digestion(s) for balance of metal(s) analysis (Method 3010/7470/7760)
- fifth step - perform metals analysis and determine metal concentrations (Method 6010-ICP/cold vapor/AA)
* any metal concentration that is less than or equal to the TCLP limit passes the TCLP test and thus helps maintain Bevill status for the kiln dust
* any metal exceeding the TCLP limit fails TCLP
Alternate Flow Chart
An alternative to using Method 3010 sample digestion for all metals but silver and mercury would be to use Method 3005 which is good for all the BIF metals except for mercury. This presents just two digestion methods for consideration rather than three and avoids any confusion concerning Antimony. The logic for this approach is based upon the preamble to the Third edition of SW-846, found in the Federal Register, whereby the analyst is allowed to choose the best method if not otherwise specified. A flow-chart has also been developed (See Figure 2) and is provided to help facilitate analytical decisions regarding this alternate option for TCLP metal leachate sample preparation and test methods. Whichever method is chosen, appropriate QA/QC (including percent recoveries of spikes) must be performed.