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Standard Interpretation

Standard: 2003 NELAC
Section:, Appendix A
Link to relevant standard


FoA Matrix states, "these matrix definitions shall be used when accrediting a laboratory"...

"Biological Tissue: any sample of a biological origin such as fish tissue, shellfish, or plant material. Such samples shall be grouped according to origin."

And, from the 2003 standards, Section "Prior to acceptance and institution of any method, satisfactory demonstration of method capability is required. (See Appendix C and In general, this demonstration does not test the performance of the method in real world samples, but in the applicable and available clean quality system matrix sample (a quality system matrix in which no target analytes or interferences are present at concentrations that impact the results of a specific test method), e.g., drinking water, solids, biological tissue and air."

The statement, "such samples shall be grouped according to their orign", confuses categorization. If a lab seeks accreditation for biological tissue matrix, is a DOC required for shellfish, plant, fish tissue, etc.? (Assuming the lab will be analyzing various types of biological tissue.)

Extending to batch QC, is the lab required to use a shellfish CRM for shellfish samples, a fish CRM for fish samples, etc.?


(Quality Systems Expert Committee and NELAP AC, 11-8-12)

When all real world materials contain target analytes and/or interferences, a "representative" matrix may be used for a given test method and analyst. If the test method as defined by the combination of preparation, cleanup and determinative methods for a given biological tissue is different from the test method (preparation, cleanup and determinative method) for another biological tissue, then separate DOCs are expected.

With regard to batch QC, it is highly improbable that CRMs exist for all biological tissues that could be analyzed. However, when available a CRM that matches the tissue type (e.g., shellfish, fish, etc.) should be used. A representative material may be used for laboratory control spikes as long as the material used follows all steps of the test method.