Proficiency tests for analysis of pesticide residues in kimchi cabbage and ginseng in South Korea from 2008 to 2020

From 2008 to 2020, the Ministry of Food and Drug Safety (MFDS) and the Korea Research Institute of Standards and Science (KRISS) jointly conducted a proficiency testing (PT) program for the analysis of pesticide residues in kimchi cabbage and ginseng powder. This collaborative effort marked a significant milestone in South Korea, being the first instance of employing metrologically traceable assigned values, determined via isotope dilution mass spectrometry (IDMS), in PT programs. The focus was on a selective range of pesticides, including diazinon, chlorpyrifos, p,p’-DDE, γ-HCH (lindane), α-endosulfan, and β-endosulfan. Each biennial PT program centered on two of these pesticides with participating laboratories reporting their mass fractions in provided samples. PT samples were prepared meticulously prepared in powder form by KRISS, ensuring homogeneity and stability, integral for the accuracy of the testing. The paper elaborates on the intricate processes involved in PT sample preparation and the rigorous assignment of values. To evaluate laboratory proficiency, the Horwitz equation was utilized as a general mode to set for standard deviations in proficiency assessment. An in-depth review of seven PT programs conducted over this period demonstrates the significant role these programs played in advancing the measurement competencies of laboratories, underscoring the novelty and impact of this long-term collaborative effort.