Standard: 2003 NELAC
Section: Appendix C.3.2 (c)
Link to relevant standard
Is it acceptable to demonstrate the accuracy and precision at the Limit of Quantitation (LOQ) using a concentration that is less than the LOQ, including down to 1/2 the LOQ?
TNI FINAL RESPONSE:
(Quality System Expert Committee/NELAP Accreditation Council, 2-10-13)
"The validity of the LOQ shall be confirmed by successful analysis of a QC sample containing the analytes of concern in each quality system matrix 1-2 times the claimed LOQ."
The standard requires concentrations that are 1-2 times the claimed LOQ. A concentration below the LOQ may not have the same accuracy and precision and therefore could not be used to verify the LOQ.