Cumulative Spectroscopic Detection for Taylor Dispersion Analysis of Nanoparticles

Taylor dispersion analysis (TDA) provides a robust approach for determining the hydrodynamic diameter of molecular objects and nanoparticles (NPs), measuring diffusion of the analyte in laminar flow through a long capillary. TDA measurements are usually performed on capillary electrophoresis equipment with in-line absorbance detection. Here, we introduce a simple, yet versatile cumulative spectroscopic detection (CSD) technique for TDA, that precisely samples the radially averaged analyte concentration flowing out of the TDA capillary. CSD can be employed in different optical spectroscopic configurations, such as absorbance, fluorescence or resonant light scattering. A theoretical model of the measurement was formulated that combines Taylor's original expression with an extended injection and then accounts for the accumulation of the analyte in the detection cell. The model was validated by comparing the hydrodynamic radii of various nanoparticle samples measured by TDA-CSD to those obtained by differential dynamic microscopy and dynamic light scattering. Beyond TDA, CSD may be useful for accurate sampling of analyte peaks in other flow-based analysis techniques, such as liquid chromatography.