In order to verify the efficacy of biochip technology in the detection of veterinary drug residues in raw milk and to promote its application, 80 common veterinary drugs in raw milk were detected by biochip and confirmed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that the limit of detection (LOD) of the biochip method met the requirements of the national standard, and the LOD for some veterinary drugs was below the national standard limits. The linear range of the method was wide, with correlation coefficient (r) greater than 0.99. Recoveries for negative samples spiked at 2 × and 4 × LOD concentrations were 70%–130%, with coefficient of variation (CV) of 5%–10%. This method has the advantages of simple pretreatment, short detection period and high sensitivity and is suitable for rapid screening of large quantities of samples. Using the proposed method, 10 of 100 batches of raw milk collected from Shanghai during 2022–2023 were tested positive for veterinary drug residues. Streptomyci was detected in 4 batches at concentration levels of 5.86–10.26 μg/kg, sulfapyridine in 3 batches at 1.09–1.42 μg/kg, sulfamonomethoxine in 2 batches at 1.38–1.46 μg/kg, and avermectin in 1 batch at 1.75 μg/kg. These concentration levels were far lower than the maximum residue limits set by international organizations, an announcement of the Ministry of Agriculture and Rural Affairs, and the national standard. Compared with traditional HPLC-MS/MS, the biochip method has the advantages of high sensitivity, wide linear range and fast detection rate. It can be used as a supplementary means for rapid detection of veterinary drug residues in raw milk, and has high application value.

In order to explore the key factors for the nutritional quality evaluation of raw milk in Shanghai, a total of 167 batches of raw milk were collected from 11 large-scale dairy farms in Shanghai from July 2022 to March 2023, and their amino acid composition, fatty acid composition, vitamins, lactoferrin and trace elements were detected. The amino acid composition data were analyzed by means of principal component analysis (PCA) and the proportions of various fatty acids were compared. The results showed that 16 amino acids, 26 fatty acids, active factors including lactoferrin, α-lactalbumin and β-lactoglobulin, and 9 essential trace elements were detected in raw milk. On this basis, we selected 13 key factors for the nutritional quality evaluation of raw milk, which could provide an important reference for the further screening and utilization of raw milk sources in Shanghai.

A proficiency testing (PT) program for the determination of aflatoxin M1 (AFM1) in milk powder was designed and conducted so as to identify the interlaboratory differences and to understand, assess and improve the proficiency of the participant laboratories. Split-level test samples were prepared according to the Guidance on Statistical Treatment of Proficiency Testing Results and Proficiency Evaluation (CNAS?CL002), and the uniformity and stability of the samples were analyzed by one-way analysis of variance and t test, respectively. Robust statistical analysis of the proficiency testing results was conducted to evaluate laboratory proficiency through Z score. The homogeneity and stability of the samples met the requirements of proficiency testing. Of 49 laboratories that reported results for AFM1 in milk powder, 45 (91.8%) performed satisfactorily. The majority of the participant laboratories passed the proficiency testing with satisfactory results, indicating that the laboratory performance for the determination of AFM1 in milk powder was generally good. The outlier results found in a few laboratories was largely ascribed to experimental operation and data processing errors.