A bovine milk reference material was produced containing amoxicillin with a target concentration at the maximum residue limit. For the evaluation and characterization of the reference material, an isotope dilution–liquid chromatography/tandem mass spectrometry method was developed and validated. This material was prepared by collecting milk samples from cows treated with an appropriate amoxicillin injection, followed by freeze-drying, dilution, and homogenization of the authentic samples. The amoxicillin reference material, prepared in accordance with ISO Guide 35, was homogeneous and stable. It was assigned a certified value of (4.10 ± 0.13) μg/kg with a relative standard deviation between 2.93 and 5.29%, which meets the maximum residue limit (MRL) requirement of 4.0 μg/kg established by the United States, the European Union, and China. This reference material can be used for method validation and provides internal quality control assurance for the detection of amoxicillin.
Wei et al. (Sun,) studied this question.