Multimethod quantification of Ag+ release from nanosilver

There is a significant interest in determining the effects of nanomaterials on the environment and human health. Part or all of the toxicity attributed to silver nanoparticles (nAg) may be due to the release of free silver (Ag+). Therefore, it is necessary to have techniques that will allow the precise determination of free Ag+ within suspensions of nAg particles. Among the different methods used for the determination of free metals in natural waters, the ion-exchange technique (IET), has promise to both distinguish Ag+ from nAg and to attain the low detection limits required for the analysis of natural samples. In this paper, IET. centrifugal ultrafiltration and single particle inductively coupled plasma mass spectrometry (SP ICP-MS) were used to determine very low concentrations of free or dissolved Ag in commercial suspensions of nAg. Dilution of the silver nanoparticles played an important role in the measured Ag+ concentrations. The relative release of Ag+ from nAg increased as samples were increasingly diluted, implying that it is critical to determine Ag+ concentrations under the precise conditions used for determinations of toxicological or environmental fate.