Solvent Enhanced Light Scattering Technique Enhances Gel Permeation Chromatography Analysis
The ideal solvent for a material may not provide a sufficient refractive index difference for light scattering detection. This example of a biodegradable polymer shows how SELS is used to increase dn/dc to give enhanced detection sensitivity
Chris Mirley, Sean Daughtry, Wei Sen Wong |
In collaboration with Metabolix
Viscotek has been a strong advocate of good chromatography as a prerequisite for GPC (Gel Permeation Chromatography) data accuracy. Our recent work in application development has been driven by extremely difficult samples from industrial, biopharmaceutical and academic sources. These samples present challenges ranging from sample solubility, column adsorption as well as detection issues. This report will attempt to highlight a new approach that will be very helpful in certain advanced GPC applications where the eluent is expensive or hazardous.
SELS emphasizes the separate and different roles of sample solvent and mobile phase in a GPC analysis where the two liquid mediums can be synergistically applied to solve a variety of chromatographic problems. (Figure 1) This is a break from tradition where most GPC analyses involve a single solvent for sample prep and as the mobile phase. In SELS, one can choose the best solvent for a set of samples in term of solubility. On the other hand, users can also maximize detector sensitivity, particularly LS, by choosing a mobile phase that will provide the highest dn/dc values for the samples. Because of the much larger volumes required for the mobile phase, material cost and HS&E properties could also be important factors. Finally, column-sample interaction can also be moderated through proper selection of the mobile phase. In general, SELS is rapidly becoming a significant parameter in GPC method development.