Development of reference methods and reference materials for trace level antibiotic residues in food using IDMS

摘要

Food additives, drugs and growth-enhancing compounds are prominent tools in the production of sufficient quantities of affordable food. Thus, food safety has become a main concern of many countries for protection of their population's health. Analytical chemical measurements are increasingly important to ensure consumer protection, particularly in the field of antibiotic residues. International comparability and reliability of measurement results can be achieved by establishing and demonstrating the metrological traceability of those results to the International System of Units (SI). To ensure the metrological traceability of measurement results, reference methods and certified reference materials (CRMs) are needed. Nitrofuran antibiotic drugs used for the treatment of bacterial and protozoan infections in animals were studied in this thesis. A high accuracy reference method and an appropriate CRM for the detection of nitrofurans in prawns have been developed.A reference method for the measurement of mass fractions of nitrofuran metabolites 3-amino-5-methyl-morpholino-2-oxazolidinone (AMOZ), 3-amino-2-oxazolidinone (AOZ), semicarbazide (SEM) and 1-aminohydantoin (AHD) has been developed utilising an exact matching double isotope dilution mass spectrometry (IDMS) method. A feasibility study on a fortified reference material was carried out by preparing fortified samples containing the four nitrofuran metabolites. The stability testing results showed that the analytes in the freeze-dried matrix were more stable than in the wet form. Freeze-dried certified reference materials of nitrofurans in prawns have been produced; an incurred AOZ (CRM_P1) and incurred AOZ and fortified SEM (CRM_P2). The reference method developed was applied for the characterisation of certified reference materials for homogeneity, stability study and certification. The prepared certified reference materials were found to be homogeneous and remained stable under normal transport conditions.The measurement uncertainty of the measurement results obtained by the reference method developed was determined by thoroughly examining all possible sources of potential bias and precision effects. An initial measurement uncertainty for certified values of AOZ in both materials has also been estimated. Metrological traceability of measurement results obtained by the developed reference method and the reference value of the prepared certified reference materials has been established through the use of the traceable primary ratio method of exact matching double IDMS, the use of certified nitrofuran metabolite standards, and gravimetric preparation of samples.