Using Standard Reference Materials
Characterization of standard reference materials is necessary to assign property values to the material. There are a number of approaches that can be taken for characterization including:
Matrix
The reference material should have a matrix as close as possible to the matrix of the material that will be subjected to the measurement process. For Example — If a laboratory wishes to validate vapor pressure in motor gasoline, then the reference material should be motor gasoline, not another matrix such as crude oil.
Level
The reference material should have properties at the level(s) appropriate to the level at which the measurement process is intended to be used. For Example — Concentration
Quantity and Container Suitability
The quantity of the reference material, the container type, and the container capacity should be in accordance with the test method requirements and include some reserve if necessary. For Example — ASTM D5191 specifies that the only valid container for obtaining samples is 250 mL or 1L containers. ASTM D3606 requires 25mL of reference material.
Acceptable Uncertainty of the Certified Value
The smaller the acceptable uncertainty value is, the more accurate the ARV is under equivalent confidence intervals.