Voltammetric detection of metal nanoparticles separated by liquid chromatography.

Fast-scan cyclic voltammetric (FSCV) detection of the separation of small (< 2-nm core diameter) organothiolate monolayer-protected gold clusters (MPCs) by high-performance liquid chromatography (HPLC) is demonstrated in this paper. Cyclic voltammograms taken at 1-s intervals (scan rate 150 V/s) display distinctive current-potential patterns for different MPCs, aiding in their identification. Previous amperometric detection of MPC separations required multiple HPLC runs at different electrode potentials to construct hydrodynamic current-potential voltammograms. Theory for ratiometric response of photodiode array absorbance and constant potential amperometry detectors was further tested on the fast-scan voltammetric detector and gave reasonable relative core size results for a mixture of Au140 and Au38 MPCs. In the first analysis of mixed MPC monolayer composition that is not simply an overall average result, preliminary HPLC experiments on MPCs with mixed hexanethiolate and ferrocenyl-octanethiolate monolayers resolved peaks that are shown to correspond to different average numbers of ferrocene-labeled ligands per MPC. Copyright 2004 American Chemical Society