Assessment of technical problems in the analysis of inorganic elements in squid through proficiency testing

Results of proficiency testing (PT) undertaken to assess the analytical skills in Japanese laboratories are presented. The PT was coordinated jointly by the National Metrology Institute of Japan (NMIJ) and the National Food Research Institute (NFRI), in which the determination of As, Cd, Fe, Mn and Zn in a dried powdered squid powder was carried out in compliance with the international standard ISO/IEC 17043:2010. A prescribed protocol for the determination of the moisture content of the sample was given to the participants beforehand. Any sample preparation/extraction methods were not prescribed, and a variety of methods was thus applied by the 118 participants. Reported results were assessed using the En-number and z-score approaches in accordance with ISO/IEC 17043 and the international harmonized protocol for PT. Results of this PT are reviewed in detail, and technical problems leading to some unsatisfactory results are discussed.