Quantifying silver nanoparticle association and elemental content in single cells using dual mass mode in quadrupole-based inductively coupled plasma-mass spectrometry.

In this study, a method of simultaneous dual mass detection for single cell analysis by quadrupole-based ICP-MS (ICP-QMS) is proposed. The method shows potential for use in quantitative investigations of nanoparticle association and elemental composition of cells. Dual mass detection had been attempted in the analysis of two-element core-shell nanoparticles and in isotope dilution analysis. In this method the detector switches between two selected masses during the analysis. Dual mass mode eliminates the discrepancies in signal that can occur due to sample instability or fluctuation in sample uptake when two masses are analysed sequentially by conventional single cell analysis (SP mode). Preliminary tests showed that using an Mg spike as marker of cells in dual mass mode was feasible for the quantification of cells. The method showed good linearity and a reproducible detection rate, and the results were comparable to the SP mode. The approach was then employed with algal cells exposed to silver nanoparticles (AgNP), to study on the Ag-associated cells and AgNP by monitoring the Ag and Mg signal in one analytical run. Finally, Mg and Mn were detected, and then quantified using the same approach to evaluate the elemental composition and correlation between different elements of the exposed cells. It is believed that this dual mass approach can extend the capability of ICP-QMS for multi-elemental detection at the single cell level, representing an enormous potential for size characterization, quantification and elemental composition evaluation in single cell (particle) analysis.