Proficiency test in Japan for the elements in tea-leaf powder

Abstract The National Metrology Institute of Japan (NMIJ) started a series of proficiency test (PT) projects, science 2009, to improve the ability to analyze the elements in environmental and food samples. The first PT was carried out for determination of selected elements (i.e. Al, Ca, Fe, K, P, and Zn) in tea-leaf powder, where a candidate reference material for trace elements in tea-leaf powder was used as the PT material. In the first PT, 41 participants registered, 38 of whom submitted 39 sets of reports. Three national metrology institutes – National Metrology Institute of China, Korea Research Institute of Standards and Science and NMIJ – carried out a co-analysis of the candidate material in parallel with the PT. Certified values, characterized based on independent measurement by NMIJ, were confirmed by the results of co-analysis and were applied as the reference values to evaluate the reported results.