The evaluation of the uptake of nanomaterials by cells in vitro tests is of great relevance to understand potential toxicity mechanisms of nanomaterials. As an example, the uptake of medium-sized nanosilver (size range of 50 and 75. nm) was studied closely for a relevant human lung cell line (THP-1). Time dependent uptake was studied in relation to different cell culture media with or without the addition of fetal calf serum (FCS). After cell isolation, washing, acid digestion and quantification of silver (Ag) by inductively coupled plasma mass spectrometry (ICPMS) were applied to study the general uptake. It is demonstrated that the uptake of Ag (from 75. nm Ag nanoparticles) is a factor of 5 higher in a medium without FCS in comparison to the medium with FCS. In addition, the stability and the abundance of Ag nanoparticles in the supernatant after cell exposure were studied in relation to different timings. By means of asymmetric flow field flow fractionation (AF4) for the size dependent particle separation and an on-line hyphenation to the sensitive elemental detection by ICPMS, different Ag particles were separated and further identified. By combining results from the total uptake of Ag by cells with results obtained from the analysis of the supernatant, total recoveries of 98 to 104% were determined in relation to the exposed concentration of Ag.Finally, the influence of the medium composition (with or without FCS) on the stability of 50. nm Ag nanoparticles was studied directly after spiking. A method by AF4-ICPMS was applied and the obtained fractograms confirm a clear influence of the different composed media composition and particle size on cellular uptake.The developed and applied ICPMS methods were found to be suitable approaches to evaluate the potential uptake of inorganic nanoparticles by cells.