An accuracy-based proficiency testing programme with metrological reference values for the mass fraction of acesulfame potassium and sucralose in cake mix flour

This paper describes a metrological approach to evaluate the measurement capability of laboratories participating in a then Asia Pacific Laboratory Accreditation Cooperation [APLAC, now Asia Pacific Accreditation Cooperation] proficiency testing (PT) programme on mass fraction of acesulfame potassium and sucralose in cake mix flour. The programme was jointly organised by the Chemical Metrology Laboratory of the Health Sciences Authority, Singapore, and the Singapore Accreditation Council. Through the extensive APLAC network of accreditation bodies, 41 nominated laboratories from 32 economies registered, of which 40 laboratories submitted their results. Reference values of artificial sweeteners in the programme for performance evaluation were obtained from a high-accuracy liquid chromatography isotope dilution mass spectrometry (LC-IDMS) method. One of the unique features of this PT programme was the provision of pure substance certified reference materials (CRMs) of acesulfame potassium and sucralose to the participating laboratories as calibration standards to ensure comparability and metrological traceability of results. The participating laboratories’ performance, based on z -scores, were evaluated using the assigned reference value determined from IDMS. Five and one of the laboratories’ results would be incorrectly evaluated using consensus value calculated from the laboratories’ results for performance evaluation and using commercial standard as calibrant, respectively. This PT programme demonstrates the importance of the use of metrologically traceable reference values as the assigned values for appropriate evaluation of accuracy and reliable assessment. The provision of CRMs also heightened the testing laboratories’ awareness on the importance of using CRMs as calibrants for accurate measurements.