What is the difference between CRM, RM, SRM, ERM & SUS?

Reference material (RM) is the generic term for a group of either pure substances or matrix materials, which are used for calibration, method validation, the establishment of metrological traceability, method development, and various quality control purposes (proficiency testing, charting, etc). If the reference material fulfils a number of requirements (proven homogeneity and stability, characterisation of the property values using suitable, well-described and validated methods) this information may be summed up in a certificate, thus being a certified reference material (CRM). SRM® is a trademark registered by the US National Institute for Standards and Technology (NIST) for the certified reference materials they produce and stands for Standard Reference Material. Any ERM® is a trademark of the European Communities for CRMs produced by partners of the European Reference Material (ERM) co-operation and fulfilling stringent quality criteria.

Reference Material Certificate - Document accompanying a certified reference material stating one or more property values and their uncertainties, and confirming that the necessary procedures have been carried out to ensure their validity and traceability. (ISO Guide 30: 1992)

Setting-up Samples (SUS) have an uncertified analysis and to be used as a guide. They are used to meet the day-to-day setting-up requirements or shift-to-shift adjustment of spectrometers or instrument for production control analysis. The quality of SUS samples is to be homogeneous.