CRM (Certified Reference Material) is a reference material with one or more property values certified by a metrologically valid procedure, accompanied by a certificate with stated uncertainties and traceability — the highest tier of reference materials used for calibration, method validation, and quality control.

CRM Characteristics

• Certified Values: Property values determined by rigorous characterization — traceable to SI units or internationally accepted standards.
• Stated Uncertainty: Each certified value has an expanded uncertainty (typically k=2, 95% confidence).
• Certificate: Official document specifying certified values, uncertainties, intended use, and expiration date.
• Traceability: Unbroken chain of calibrations linking the CRM to primary standards — metrological traceability.

Why It Matters

• Calibration: CRMs are used to calibrate analytical instruments — ensuring measurement accuracy and traceability.
• Method Validation: CRMs verify that a measurement method produces accurate results — the "known answer" test.
• Regulatory: Some measurements (environmental, clinical) legally require the use of CRMs for calibration.

CRM is the gold standard sample — a reference material with certified property values and traceable uncertainties for reliable calibration and validation.