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Standard Interpretation



SIR #: 109
Standard: 2003 NELAC
Section: Appendix C.3.1 (b)
Link to relevant standard

REQUEST:

LOD verification: For our lab, MDL is the LOD. Once an acceptable LOD is established via MDL, if the spike used meets the LOD spike concentration criteria (2-3X the LOD of the single analyte), is it necessary to prep and analyze another sample, or can one of the replicates analyzed for the MDL determination itself can be considered as a verification of the LOD?

TNI FINAL RESPONSE:

Draft Response: C.3.1 b) only states that the LOD must be verified on each instrument used for reporting data. It doesn't place a limit on when that must happen. Therefore, if one of the replicates analyzed for the MDL determination meets the applicable criteria for LOD verification, that would meet the intent of the Standard.

Revised QS Response: C.3.1 b) only states that the LOD must be verified on each instrument used for reporting data. It doesn't place a limit on when that must happen. Therefore, if one of the replicates analyzed for the MDL determination meets the applicable criteria for LOD verification, that would meet the intent of the Standard. The value of the spike used to calculate the MDL must be at no more than 2-3x the calculated MDL. It is expected that all of the replicates in such a study would show a recovery to be used to calculate the MDL.