Inter-Laboratory Analysis Program
The purpose and scope of this specification is to define certain terminology, procedural techniques, criteria and protocol to be utilized by members of the ongoing "Inter-laboratory Analysis Program" (ILAP) conducted by Analytical Reference Materials International as it applies to the development, certification and production of certified reference materials.
The International Standards Organization (ISO) definitions, expressed in ISO Guide 301992 Second Edition list the following:
Certifying Body - A technically competent body (organization or firm, public or private) that issues a Reference Material Certificate which provides the information detailed in ISO Guide 31.
Reference Material (RM) - Material or substance with one or more properties 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.
Certified Reference Material (CRM) - Reference material, accompanied by a certificate, one or more of whose properties 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.
ASTM Standard E691-87 applies to Inter-laboratory studies to "Determine the Precision of a Single Test Method". This standard is also a well thought out and logical plan for conducting an Inter-laboratory program involving multiple techniques. Therefore, the planning, conducting, analyzing, protocol and treatment of data resulting from the ARMI\ILAP is performed utilizing the guidelines established in ASTM E691-87 where applicable.
Selection of Participating
ILAP membership is voluntary and consists of approximately 60% actual producers of the materials being analyzed, 30% technically qualified commercial laboratories and 10% representing general industry and academia.
Materials are typically selected from standard industry stocks so as to emulate material types found in the real life circumstances dealt with by users in their daily analytical endeavors. Whenever possible, program materials are secured in a wrought condition. Other methods of manufacture such as continuous cast, sand or static castings are utilized as a last resort and only in the case of those materials being unavailable in wrought condition.
Since most metals are available in bar stock or rod form, a typical "batch" or "series" is defined as a single length of material or a single bar of one continuous length.
The "batch" samples are taken by dividing the bar into a minimum of twelve sub-sections. A one inch solid test sample is removed from each sub-section. Each one inch test sample is further subdivided as follows: The "batch" samples are taken by dividing the bar into a minimum of twelve sub-sections. A one inch solid test sample is removed from each sub-section. Each one inch test sample is further subdivided as follows:
Approximately 12.5% (.125 in.) of the total sample is converted to chip form for analysis by classical wet chemistry, ICP, AA, and combustion procedures.
An additional 12.5% (.125 in.) is converted to the form of solid pins for determination, when appropriate, of C, S, N2 and O2 by combustion procedures.
The remaining 75% (.75 in.) of each sample remains in a solid disk form for Optical Emission and X-Ray analysis where applicable.
Each member of the "Inter-laboratory Analysis Program" receives the three sample types and is therefore responsible for a specific sub-section of the batch bar. All sub-sections and corresponding test samples are sequentially marked with matching and unique internal identification numbers so that if abnormalities occur during the ILAP process, each test sample can be traced to the original sub-section. Due to this extensive sampling procedure, homogeneity of the total batch is therefore reflected as a product of the overall statistics and the resulting certified data.
Specific Within Sample
Determination of Homogeneity
Effective with materials certified after 10/20/91, specific homogeneity testing is determined by the ILAP program management, and incorporates homogeneity test procedures as outlined in ASTM E-826-87, NBS Handbook 91, "Experimental Statistics", as well as other established practices for determination of practical homogeneity.
Methods of Analysis
The ARMI "Inter-laboratory Analysis Program" encompasses an extremely wide variety of materials. No single method would provide optimum data results. Therefore, the methods utilized are a combination of methods for classical wet chemistry, ICP, AA, Optical Emission and X-Ray spectrometric methods in addition to combustion procedures for the determinations of Carbon, Sulfur, Nitrogen and Oxygen.
Extent of Data Reported
It is the policy of Analytical Reference Materials International to report data submitted by two or more labs. However, in accordance with the guidelines established by the ILAP membership protocol, final certification occurs only for those elements in which a minimum of six data points remain after final critique. Therefore, data in parentheses ( ) is not certified but provided for information only. Certified Data that was selected by the ILAP membership for additional testing is indicated by brackets [ ].
Traceability to NIST is approached in two distinct ways within the ARMI\ILAP.
SRMs produced by the National Institute of Standards & Technology (NIST) are selected by ARMI on a "best available/matrix compatible" basis. ARMI removes the NIST identification, converts portions of the solids to chip form and re-labels both the solids and the chips with unique ARMI identification. These materials are then submitted to ILAP members as "unknowns" for analysis at the expense of ARMI. The resulting data from this procedure is compiled, statistically evaluated and archived in the historical database.
In the case of some matrix groups, specific SRMs are not always available. In this case, the ILAP program members voluntarily make available to the ILAP a variety of SRMs produced by (NBS\NIST), some of which have been collected over almost two decades. In addition to validating test methods and instrument performance, where possible, these resident SRMs are also used in the instrumental calibration curves for that portion of the ILAP which requires instrumental analysis. Affidavits of the ILAP member labs' SRM inventory and their applications are on file and archived in the ARMI historical database.
The analytical data results for the IARMs developed under this program are therefore "Traceable" to the U.S. Department of Commerce, National Institute of Standards & Technology, (NIST). The specific SRMs applicable to a certification are referenced on the face of the "Certificate of Analyses" for all ILAP certified materials.
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