ANYL 284 |
| Photon correlation spectroscopy (PCS) or dynamic light scattering is a batch mode method commonly used to measure diffusion coefficients (D) of macromolecules and nanoparticles. This technique is based on the measurement of fluctuations in light intensity that arise from the Brownian motion of particles suspended in a fluid. By measuring the time dependence of light intensity fluctuations about an average intensity (autocorrelation function versus time), it is possible to determine diffusion coefficients. The time needed to acquire sufficient measurements to establish the autocorrelation function is dependent on particle size and concentration. In the last five years, a number of manufacturers have begun offering flow-through PCS as a detector for elution based separation methods. The effluent exiting a size exclusion column or a field-flow fractionation channel is moving at a velocity determined by the flow rate used to accomplish the separation. In other words, there is a translational motion down the separation axis in addition to the random particle motion. The question that needs to be answered is whether the D measurements obtained by flow-through PCS are accurate under all separation conditions. We have undertaken a study to compare D values obtained by batch mode and flow-through PCS. The effects of flow rate and analyte concentration and molecular weight have been investigated. These results have enabled us to define guidelines for accurate PCS operation. |
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Analytical Approaches: Separation Science
1:30 PM-5:00 PM, Wednesday, 13 September 2006 Moscone Center -- Room 130, Oral
Division of Analytical Chemistry |