The materials and checks that allow an analytical run to be interpreted with confidence.
Reference standards
A reference standard should be sufficiently characterised for its use. The required knowledge of identity, purity or content depends on whether it supports identification, quantitation or performance control. Origin and storage conditions should be documented.
System suitability
System-suitability tests check before or during a run that the complete system can produce acceptable data. Examples include repeatability, resolution, tailing or response. Criteria should have a scientific basis and be predefined.
Blanks, positive and negative controls
A blank can reveal contamination or background, while positive and negative controls test whether the procedure distinguishes expected states. A failed control is not fixed by selecting favourable results; it requires investigation and a documented decision on the run.