certified reference material

**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.