Non-toxic and potentially toxic elements in Italian donkey milk by ICP-MS and multivariate analysis

Concentrations of 6 non-toxic and 6 potentially toxic elements in donkey milk, forage and feed samples from 3 Italian farms were determined by ICP-MS. Zn (mean value range: 1.403–4.567 mg kg−1) and Fe (0.733–2.220 mg kg−1) concentrations were the highest in all analyzed milk samples, followed by Cu (0.125–0.199 mg kg−1), Mn (0.024–0.046 mg kg−1) and Se (0.030–0.040 mg kg−1). In consideration of the foregoing and of the RDA values, donkey milk appears a good source of selenium for both adults (3.64–23.27%RDA) and children (20–128%RDA). Furthermore, the majority of samples did not reveal residues dangerous for human health. Indeed, Hg (0.96–1.22 μg kg−1) and As (42.84–78.05 μg kg−1) are within the prescribed range, while Cd (3.96–11.19 μg kg−1) and Pb (9.77–18.11 μg kg−1) were, at times and only for children, above the respective benchmark. In 11% of total milk samples Pb levels exceed the European limit (0.02 mg kg−1), while Sb (28.77–38.04 μg kg−1) and Ni (30.00–36.00 μg kg−1) levels could not be compared due to the lack of available parameters. Data were analyzed by chemometric assessment to elicit the correlation within the different samples and to evaluate statistically significant differences among samples from the farms and seasonal variations during the sampling periods. Findings have established the geographical origin of milk on the basis of the mineral profile and can be used as a tool to elicit the authenticity of donkey milk.