Difference between Consensus Value of Participants’ Results and Isotope-Dilution Mass Spectrometric Results in Proficiency Testing for Pesticide Residues in Husked Wheat

• Published in: Analytical Sciences Vol. 32; no. 5; pp. 557 - 580
• Main Authors: YARITA, Takashi, OTAKE, Takamitsu, AOYAGI, Yoshie, NUMATA, Masahiko, TAKATSU, Akiko
• Format: Journal Article
• Language: English
• Published: Singapore The Japan Society for Analytical Chemistry 2016; Springer Nature Singapore; Japan Science and Technology Agency
• Subjects: Analytical Chemistry; assigned value; Chemistry; Consensus; Deviation; Humans; Isotopes - analysis; Japan; Laboratory Proficiency Testing; Legislation, Food; Malathion - analysis; Mass spectrometry; Mass Spectrometry - standards; Mathematical analysis; Metrology; Performance evaluation; pesticide; Pesticide Residues - analysis; Pesticides; primary method of measurement; Proficiency testing; Research Design; Residues; Triticum - chemistry; water-soaking; Wheat; z-score; score; primary method of measurement; Proficiency testing; pesticide; water-soaking; assigned value
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.32.557

Proficiency testing was organized by the National Metrology Institute of Japan (NMIJ) as a measure of analytical competency in the quantification of pesticide residues in husked wheat powder. Seventy-one participants submitted analytical concentrations of the target pesticides (diazinon, fenitrothion, malathion, and etofenprox) along with details of the analytical method employed. Two types of assigned values were obtained for each target pesticide, i.e., the participants’ analytical results and the results obtained by NMIJ based on isotope-dilution mass spectrometry (IDMS). The former values were lower than the latter due to the incomplete recovery yield of the target pesticides during the pretreatment process. The discrepancy between the two assigned values was particularly pronounced for malathion because of the longer duration of water-soaking used for the test samples. Two corresponding types of z-scores were then calculated to evaluate the analytical performance of the participants, where the z1-score indicates the performance of a participant relative to all participants, and the z2-score indicates the relative deviation of the analytical results of the participant from the IDMS value.