Implementation of the ISO 33405 requirements and production of a certified reference material for nitrofuran metabolites as incurred chicken muscle.

Certified reference materials (CRMs) contribute to the traceability of measurement results to recognized anchor points, ideally to the International System of Units (SI), and consequently, to their comparability and reliability. In the area of veterinary drugs' residues in foods of animal origin, the important role of CRMs must be highlighted, given the problems caused by trade restrictions in some countries. The results of studies concerning the certification of an incurred matrix certified reference material (IMCRM) for the mass fraction of nitrofuran metabolites in chicken muscles are presented in this work. A batch of IMCRM candidates was produced from chicken muscle samples containing the metabolites 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), semicarbazide (SEM), and 1-aminohydantoin (AHD). All the statistical approaches for the homogeneity and stability assessments were based on the principles contained within ISO Guide 35 (current ISO 33405:2024). All the quantitative analyses of the nitrofuran metabolites were performed by means of high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The properties studied were sufficiently homogeneous and stable at -20 °C for 360 days (the defined storage conditions). Under transport conditions, the AOZ metabolite showed instability at 50 °C. The residual moisture content was also monitored and showed instability at 20 °C and 50 °C. The characterization was performed via an exact matching calibration approach and the assigned values with their respective expanded uncertainties (k = 2) were 5.40 ± 1.2 ng g, 5.49 ± 0.85 ng g, 5.08 ± 1.2 ng g, and 6.01 ± 0.85 ng g for the metabolites AOZ, AMOZ, AHD, and SEM, respectively, in the lyophilized chicken muscle. These values ranged from 1.3 to 1.5 ng g on a wet basis. The expiration date for the CRM was estimated based on the stated limits for future values calculated from the confidence interval of the stability study's linear regression curve.