A quantitative multi-residue method that includes 13 sulfonamides, trimethoprim and dapsone was developed and validated according to Commission Decision 2002/657/EC for muscle, milk egg and honey samples. For all matrices, the same extraction procedure was used. Samples were extracted with an acetone/dichloromethane mixture and cleaned up on aromatic sulfonic acid (SO3H) SPE cartridges. After elution and concentration steps, analytes were identified and quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Data were acquired according to the multiple reaction-monitoring approach (MRM) and analytes were quantified both by the isotope dilution and the matrix-matched approaches calculating the response factors for the scanned product ions. The developed method shows good linearity, specificity, precision (repeatability and within-laboratory reproducibility), and trueness. Estimated CCβ for sulfonamides ranged between 5.6 and 8.2 µg kg(-1) for eggs, between 11.1 and 69.9 µg kg(-1) for milk, between 64.7 and 87.9 µg kg(-1) for muscle, and between 2.7 and 5.3 µg kg(-1) for honey. CCβ values for dapsone were 3.1, 0.6, 0.7 and 1.5 µg kg(-1) and for trimethoprim were 3.1, 6.7, 81.7 and 3.0 µg kg(-1) calculated for eggs, milk, muscle and honey, respectively. Recovery for all matrices was in the range from 89.1% and 109.7%. In matrix effect testing, no significant deviations were found between different samples of muscle and milk; however, a matrix effect was observed when testing different types of honey. The validation results demonstrate that the method is suitable for routine veterinary drug analysis and confirmation of suspect samples.
This study’s objective was to estimate the seasonal occurrence of aflatoxin M1 (AFM1) in cow’s milk between winter 2016 and winter 2022 and to assess dietary exposure and risk assessment for the adult Croatian population. In total, 5817 cow milk samples were screened for AFM1 concentrations using the enzyme immunoassay assay (ELISA). For confirmation purposes of AFM1 concentration above the European Union maximum permitted level (MRL), ultra high-performance liquid chromatography with tandem mass spectrometry was performed. In 94.7% of milk samples, AFM1 levels were below the detection limit (LOD) of the ELISA test. For 3.47% of samples, the AFM1 was between the LOD and MRL values. Only 1.87% of all samples exceeded the MRL. The mean value of elevated AFM1 in different seasons ranged between 59.2 ng/kg (autumn 2017) and 387.8 ng/kg (autumn 2021). The highest incidences of positive AFM1 were determined in autumn and winter and the maximum (6.4%) was in winter 2019/2020. The largest percentage of positive samples (69.7%) was found in central Croatia. The estimated daily intakes for positive samples ranged between 0.17 and 2.82 ng/kg body weight/day. Risk assessment indicated a high level of concern during autumn and winter, especially for consumers of large amounts of milk.
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