Testing the testers

In the recent evaluation of mineral industry standards, questions were raised about the reliability of assays. Now in its fourth year, The Proficiency Testing Program — Mineral Analysis Laboratories (PTP-MAL), run by a group within Natural Resources Canada, gives the industry and the public increased confidence in the laboratories participating in the program.

Many Canadian commercial laboratories have been registered voluntarily to the International Standards Organization’s ISO 9002 standard on quality management. The ISO 9002 registration requires that laboratories document their procedures and implement internal quality control. However, the level of confidence of the analytical procedures and of the quality control program depends mainly on the technical quality of the staff of the laboratory, which varies from laboratory to laboratory.

Monitoring of performance through participation in round robins is an additional indicator of laboratory competence. In Canada, the PTP-MAL, operated by the Canadian Certified Reference Material Project (CCRMP) in co-operation with the Standards Council of Canada (SCC), a Crown corporation, provides this proficiency testing for mineral analysis laboratories. Laboratories that are accredited for mineral analysis by SCC to ISO/IEC Guide 25 (replaced by the Standard ISO/IEC 17015) must demonstrate acceptable performance in PTP-MAL. To achieve accreditation, a laboratory must demonstrate acceptable performance in three consecutive “cycles.”

Laboratories pay about $900 annually to PTP-MAL to report their results for each of gold, silver, copper, zinc, lead, nickel, cobalt, platinum and palladium in up to four samples for analysis every six months. PTP-MAL then compares each laboratory’s results with the consensus values and reports on which results were acceptable. PTP-MAL also forwards information on performance to SCC for laboratories that are accredited to ISO/IEC Guide 25 by SCC. A lab can have its accreditation suspended for unsatisfactory performance or failure to participate.

The CCRMP has offered PTP-MAL since 1997, and there are now almost 50 labs participating. About two-thirds of the laboratories are Canadian, which include some mine site laboratories. During this period, almost 95% of the results were classified as “satisfactory.”

A proficiency testing program is a competitive process which, because of the statistical approach, leads to some analytical results being assessed as “questionable” or “unsatisfactory.” Most of these results are still of sufficient quality for practical use.

The PTP-MAL results have been encouraging and have improved confidence in participating commercial laboratories. However, the high quality of laboratory performance on known standards may not always reflect the quality of results for routine analysis, and mining companies still have an obligation to implement their own systems of quality control. Even in the PTP-MAL, there are usually, in each cycle, one or two cases in which results are reported against the incorrect sample.

Mining companies should request proof from labs that their Guide 25 accreditation is still in good standing and that their performance is “good” for commodities of interest.

— The author is president of Toronto-based Analytical Solutions, a consulting firm.