ISO Guide 34 Inorganic Standards Certified Reference Materials

Guide 34 Standards are Certified Reference Materials (CRMs) that have a claim of traceability to a national or international standard supported by evidence of stability and homogeneity which gives the analyst confidence that the analytical data derived from there use may be verified and validated.

“To support a claim of traceability, the provider of a measurement result or value of a standard must document the measurement process or system used to establish the claim and provide a description of the chain of comparisons that were used to establish a connection to a particular stated reference”.

Certification: Surprisingly few manufacturers offer standards that provide the relevant credentials to support you and your analytical results, and able to offer a range of standards with fully comprehensive and compliant Certificates of Analysis. 

With the development of laboratory accredited schemes based on ISO17025:2009 or other equivalent national standards laboratories have a need to calibrate methods against certified reference materials (CRM) through which the test results may validated to internationally traceable values (SI Units). 

Accredited Standards offer CRMs supported by the most comprehensive certification which may be considered as insurance that your analytical data meets your agreed metrics

ISO Guide 31 sets the standard for Guide 34 accredited manufacturers to properly prepare 

a Certificate of Analysis (CoA). 

A standardised CoA must accompany any Certified Reference Material (CRM). 

The certificate of Analysis should include: 

• Name and address of certifying body 

• Title of the document: Manufacturers that issue "provisional" certificates tend to confuse clients with information that is incomplete or improperly validated. Some organizations issue "Certificates of Compliance." These documents fail to cite actual lot inspection data, instead reporting historical developmental data. Such variations of the Certificate of Analysis are not ISO Guide 31-compliant and should be approached with caution. 

• Description of the material: Name of the CRM (Chemical Reference Material) and its concentration - the type of Reference Material should be identified with sufficient detail to distinguish it from similar materials. The name and the concentration of the matrix should also be clearly listed and quantified. 

• Reference material code and lot number: Every CRM has a unique code (catalogue number) that distinguishes it from all other CRMs. Additionally; a unique Batch Number (lot number) is assigned to every batch. 

• Description of CRM: The truest measure of purity is to know precisely how clean the CRM in the bottle really is. Knowing that there are low impurities is not enough. Analyzing for Trace Metallic Impurities (TMI) and listing the data of all traces gives scientists a much greater understanding of the solution`s purity. Although this is not required by ISO, this information within an informational TMI chart provides a complete picture for the analyst. 

• Intended use: The primary purpose for which the CRM is issued should be stated directly on the certificate. 

• Instruction for the CRM’s correct use: Usage instructions are included on the Certificate of Analysis and in the accompanying Material Safety Data Sheets (MSDSs). It is strongly recommended that the reference material be used under the conditions and in the sequences described in the Certificate. 

• Hazardous Information: Safety information on the certificate must be accompanied by a Material Safety Data Sheet (MSDS). The MSDS details the nature of any hazard and appropriate precautions for avoiding said hazard. 

• Level of Homogeneity: A solution`s homogeneity data appears in this section. 

• Certified Values and their uncertainties: must be carefully defined for every product. All significant errors are factored into the Uncertainty Budget. Every CRM must have a stated Uncertainty that is defined on the Certificate of Analysis.

Your results are only meaningful if reliable reference materials are used to calibrate your instruments – Accredited Standards (AS) brand are now one of the very few fully compliant manufacturers who are able to offer a range of inorganic standards suitable for all methods with fully comprehensive and compliant Certificates of Analysis giving a 100% satisfaction guarantee to the quality of our products

Expiry date: this refers to the expiry of the certificate. Once the container has been opened, and assuming the analyst has adopted “Good practice in using the reference material” in accordance with the guidelines of ISO Guide 33, the certified value assigned maybe considered as valid the period stated on the certificate. 

When you use a standard for longer than a year, you are gambling that absolutely nothing has inadvertently affected the chemical components.

 Shelf life: This is the period of time that the manufacturer may store the product under controlled conditions before the product requires re-certification. This is not the period of certification or stability once delivered to the end user.

As your results have been derived from using a reference standard, what level of confidence do you have that the standard you are using is correct, and how have you confirmed this?

ISO Guide 34 "General Requirements for the Competence of Reference Materials Producers"

Accredited Standards meet every requirement for the competence in the very specific field of Reference Material Production and have certification to ISO Guide 34.

The adoption of reference materials with ISO 17025 Guide 34 compliance assures your laboratory is able to demonstrate traceability between measured results of the measured standard references, and that of the measured sample, allowing your laboratory to achieve measurement targets, saving time and money, and more importantly giving confidence in your analytical data 

Guide 31 - Contents of certificates and accompanying documentation

Accredited Standards documentation provides in summary form all the information needed by the user of the (certified) reference material, and is considered as the most informative in the industry.

Guide 35 - Reference materials - General guidance for the assignment of property values 

In compliance with Guide 35 Accredited Standards approach for the assessment of homogeneity, stability, and the characterisation of reference materials, is well established and goes beyond what is required. Through the calculation of uncertainties of the assigned values by at least two methods and the additional analytical data which provides extended indicative information Accredited Standards are able to demonstrate excellent metrological traceability of assigned values, in addition to confirming they are “fit for purpose”

Accredited Standards have Traceability to NIST Standard Reference Materials (SRM) the detail of which is included on each Certificate of Analysis (COA) where not only the SRM number (required) but also the specific lot number (not required) of the SRM is shown on the Certificate of Analysis.

To support a claim, the provider of a measurement result or value of a standard must document the measurement process or system used to establish the claim and provide a description of the chain of comparisons that were used to establish a connection to a particular stated reference. 

There are several common elements to all valid statements or claims of traceability:

• A clearly defined particular quantity that has been measured.

• A complete description of the measurement system or working standard used to perform the measurement.

• A stated measurement result or value, with a documented uncertainty.

• A complete specification of the stated reference at the time that it was compared to the measurement system or working standard.

• An `internal measurement assurance` program for establishing the status of the measurement system or working standard at all times pertinent to the claim of traceability.