A Statistic That Identifies Errant Standard Preparation and Instrument Non-linearity Demonstrated With Mercury Standards Prepared by Blending NIST Fossil Fuel CRMs of Similar Matrices
Bruce S. MacDonald, John L. Molloy, Stefan D. Leigh, William R. Kelly, Andrew L. Rukhin
Interval-repeatability (Ir) is a statistic that users of certified reference materials (CRMs) may employ as a quality control check to identify incorrectly prepared working standards or nonlinear instrument response over a targeted concentration interval based upon an established repeatability limit (r) of the analytical method used. It is applicable to working standards prepared by CRM dilution, as well as those prepared by CRM blending. Essentially, Ir measures the repeatability of standards across a concentration interval. For the measurements of standards to comply with the method precision requirements, the absolute value of Ir(i,ii) must be less than or equal to the analytical methods Interval-repeatability Limit (r(i,ii)) for the concentration interval i,ii. Hence conceptually, Ir(i,ii) is analogous to r observed, as r(i,ii)is to the methods stated repeatability limit, r. The theory behind this approached is discussed, detailed instructions on its implementation are given, and Ir QC test data for blended mercury in coal CRMs are presented.
, Molloy, J.
, Leigh, S.
, Kelly, W.
and Rukhin, A.
A Statistic That Identifies Errant Standard Preparation and Instrument Non-linearity Demonstrated With Mercury Standards Prepared by Blending NIST Fossil Fuel CRMs of Similar Matrices, Energy and Fuels
(Accessed September 28, 2023)