Real-Time Size Discrimination and Elemental Analysis of Gold Nanoparticles Using ES-DMA Coupled to ICP-MS for Biomedical Applications
De-Hao Tsai, Sherrie Elzey, Lee L. Yu, Michael R. Winchester, Michael E. Kelley, and Vincent A. Hackley
In this study, a hybrid instrument was developed to characterize nanoparticles. Real-time particle size discrimination was achieved using an electrospray coupled to a differential mobility analyzer (ES-DMA). The ES-DMA was coupled to two detectors: a condensation particle counter (CPC) for particle concentration measurements and an inductively coupled plasma mass spectrometer (ICP-MS) for quantitative elemental analysis. A gas-exchange device (GED) was designed to convert the air flow from the electrospray to an argon flow for ICP-MS analysis. The individual components and the hybrid instrument were tested, optimized, and validated for the real-time characterization of gold nanoparticle suspensions. The GED was systematically studied to optimize exchange efficiency and particle transport. A range of gold concentrations was used (5 to 250 μg/g) to calibrate detectors. By combining the data obtained from the CPC and the ICP-MS using ES-DMA sample introduction, the hybrid instrument can provide real-time quantitative elemental analysis of size-resolved nanoparticles. This is a powerful measurement technique for the simultaneous characterization of particle size and elemental composition. Moreover, it can be further optimized for analysis of more complex colloidal systems, such as core/shell particles and particle–ligand conjugates. The advantages, challenges, and potential biomedical applications of this measurement technique are discussed.