What is the procedure when matrix interference effects cause elevated TCLP Lower Limit of Quantitation (LLOQ) that are above the TCLP regulatory limits?
For example, if you analyze a soil sample for TCLP SVOCs and you have a LLOQ for 2,4‐Dinitrotoluene (D030) of “<2.0 mg/L,” how is this handled if the TCLP regulatory limit for 2,4‐Dinitrotulene is 0.13 mg/L? Based on generator knowledge, you know that there should be no 2,4‐Dinitrotoluene at the site ‐ however you can’t disprove a negative since the LLOQ is higher than the TCLP regulatory limit for this constituent.
According to Table 7‐1 footnote (2) in Chapter Seven of SW‐846, www.epa.gov/sites/production/files/2015-10/documents/chap7_0.pdf, several contaminants, including 2,4‐dinitrotoluene, have quantitation limits greater than the calculated regulatory level. In such cases, the quantitation limit becomes the regulatory level.
However, for this to be valid, the laboratory should take every step possible to keep the reporting limit as low as possible (e.g., avoid unnecessarily high sample dilutions, use a clean‐up method, etc.).
For analytes not covered by the footnote, it is expected that the laboratory will use analytical procedures that achieve quantitation limits at or below the regulatory level.