Abstract
On the basis of two in vivo experiments involving pigs and chickens, where animals were fed with feeds supplemented with a silver-kaolin nanomaterial as a growth promoter, the fate of the ingested silver, its accumulation in different tissues and excretion, and its occurrence as ionic or particulate forms has been studied. Inductively coupled plasma mass spectrometry (ICP-MS) in conventional mode was used for the quantitative determination of total silver in the different tissues and feces. Results showed that silver accumulated in liver (0.15-5 mg kg(-1)) and kidney (0.4 mg kg(-1)) but not in muscle, while the major part of silver was eliminated through the feces (75-1026 mg kg(-1)). Laser ablation coupled to ICP-MS (LA-ICP-MS) in a conventional mode revealed a preferential accumulation of silver in the outer layer of the liver lobules in pigs. LA-ICP-MS in single particle mode (LA-SP-ICP-MS) was applied to the analysis of tissues and feces to obtain speciation information about the presence of ionic and particulate silver in the samples. Silver found in the pig liver was present in ionic form, confirming that silver was absorbed in the intestine in this form. The analysis of pig feces confirmed the presence of both ionic silver and particles containing silver with average masses of 520 ag (equivalent to solid spherical silver nanoparticles of 50 nm diameter).