Standard: 2003 NELAC
Section: Appendix C.3.5
Link to relevant standard
LOD/LOQ Question: Routine samples for TKN are analyzed daily with an automated distillation titration apparatus. Typical results are 15 to 30 ppm based on a 100 mL digestion. MDL studies of LFB samples @ 2.5 ppm yield results too little variation for valid LOD/LOQ values. However, this lab never sees samples at this low in the range. Do the sections cited above relieve the lab from performing any further MDL's? Can the laboratory state it will not report any values lower than say 5 ppm or some other conservative value?
I would very much appreciate your advise - Thank you
TNI FINAL RESPONSE:
(Quality System Expert Committee/NELAP Accreditation Council, 2-10-13)
C.3.1 c) states in part 'An LOD study is not required for any component for which spiking solutions or quality control samples are not available such as temperature, or, when test results are not to be reported to the LOD (versus the limit of quantitation or working range of instrument calibration)...' The NELAC Standard doesn't require any LOD determinations unless data are reported below the LOQ, AND a spiking solution or quality control sample is available. If the laboratory SOP or QA Manual states that this analysis is not reported below the LOQ, then an LOD is not required by the Standard. If more stringent standards or requirements are included in a mandated test method or by regulation, the laboratory shall demonstrate that such requirements are met.