Proficiency testing metrology

Extension into physical metrology is less obvious, but has no conceptual barrier. The direct approach could be applied if proficiency tests were conducted by a reference laboratory distributing to device producers, preparing lots of material measures and calibrants such as gage blocks, masses, or thermometers. Distribution of such material measures is already a feature of most measurement assurance programs in physical metrology. Use of the indirect approach would have units randomly selected from production and sent to a reference laboratory. This could prove, in some cases, more economical than direct proficiency testing of the producers of the devices. 

This paper has described new approaches to providing quality assurance within the operation of proficiency evaluation programs. The approaches are used in a new NIST program to monitor providers of proficiency testing in an environmental field. A part of that monitoring is conducted by means of indirect proficiency evaluation of the providers. The new program demonstrates that both direct and indirect proficiency evaluation can provide traceability links, in chemical metrology, to measurements carried out at NIST. 

Achieving traceability in chemical measurement - a metrological approach to proficiency testing... 

Keywords Traceability Metrological Chemical Proficiency Testing... 

To enable participating laboratories to assess their performance relative to domestic and international peer laboratories and hence to improve the comparability of results between laboratories and between countries To develop and promote a fit for purpose and affordable metrological approach to proficiency testing. 

Considering the metrological structure, a proficiency testing scheme was organised with laboratories working in water analyses. It was decided to choose a deionised water spiked with heavy metals (at 5 and 20 g/L for cadmium and lead, respectively) for the round robin test. A matrix CRM (groundwater containing cadmium and lead) was also sent to laboratories. Laboratories have been asked to analyse, in duplicate, the spiked water... 

The certified pure solutions of cadmium and lead have demonstrated the reliability of calibrations performed by laboratories. No bias was observed with the commercial or in-house solutions used by the participants of the proficiency testing. In this case, it demonstrates that there is no particular benefit for laboratories to carry out analyses using metrological-... 

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