CERTIFIED REFERENCE MATERIAL (CRM): Reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to an accurate realization of the unit in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence. The CRMs are certified by a recognized certifying organization using approved certification procedures as instructed in the most recent ISO Guide 35. The organization is usually a function of a federal government or recognized by a federal government or an accreditation organization. A CRM is the highest level to which an analytical reference material can be elevated because it is directly traceable to SI units and because of the attributed confidence in the company or organization which produced the material. Materials produced by national metrological laboratories (NML) such as NIST and ECRM are automatically CRM by default authority, it should be noted that often these NML certificates do not comply with modern expectations, but they remain CRM by default authority. |
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REFERENCE MATERIAL (RM): A material substance one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials. The RMs have been through interlaboratory testing using many analysts. |
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SETTING-UP SAMPLES (SUS): Materials which have an uncertified analysis to be used as a guide. These materials are assigned values for each element during calibration of the instrument with CRMs and RMs. These assigned values are used for day-to-day or shift-to-shift adjustment of the instrument. This process is often called "drift correction", "standardization of the calibration", or "re-standardization". Users are advised to obtain a reasonably long term supply of each SUS to avoid having to recalibrate the instrument when the current SUS supply is exhausted. |