Single particle analysis using time-resolved ICP-MS

Complete text of publication follows. It is of growing interest to characterize the metal contents of individual biological cells, nanostructures and even the functional groups of proteins. The particles can be introduced into the ICP individually and the metal contents of each particle are determined by time-resolved ICP-MS. However, detection of trace metals in the particles can be challenging (F. Li et al., Anal. Chem., 77 (2005) 1407-1413). Space charge effects in ICP-MS may also limit the accuracy of the measurement. In this study, the strategy of single particle analysis using time-resolved ICP-MS is examined. Nanoparticles of metal oxides, polyelectrolyte complexes and algal cells were used as test particles. The particles were suspended in water and introduced into the ICP using conventional solution nebulization. At particle number density of 1 x 106 ml-1, each aerosol contains no more than one particle. The particles are introduced into the ICP individually. Each particle in ICP produces a plume of analyte ions which are detected as a current spike in the mass spectrometer. The experimental setup for sample introduction and ion detection will be discussed. Strategy to enhance the detection sensitivity of trace metals in the particles and improve the accuracy of the measurement will also be discussed. The authors kindly acknowledge the financial support from the Department of Chemistry of The University of Hong Kong and the Committee on Research and Conference Grants.