text: The preparation of certified reference materials is described in general in ISO Guide 17034 and in more detail in ISO Guide 35. Preparation of biological reference standards is described in WHO Guidance. General steps required in production of a certified reference material typically include:
  * Collection or synthesis of material
  * Sample preparation (including homogenization, stabilization, bottling etc.)
  * Homogeneity testing
  * Stability assessment
  * Value assignment ("characterization" in ISO REMCO terms).
  In addition it may be important to assess the commutability of a reference material; this is especially important for biological materials.