Traditionally, online comprehensive two-dimensional liquid chromatography (2D-LC) has been used in the analyses of complex mixtures for its gain in total peak capacity and therefore the ability to reveal “hidden” peaks. In spite of the improved peak capacity with 2D-LC, the longer analysis time has been hindering wide adoption of this technique in fast-paced industry settings. Analysis of synthetic polymers often adopts size exclusion chromatography (SEC) and interactive high performance liquid chromatography (HPLC) as the two dimensions to reveal molecular weight and chemical compositional distributions, respectively. This work introduces improvements in the efficiencies for the SEC and the LC dimensions with enhanced understanding of the separation mechanisms by using advanced detection methods. In this work, sub-3 micron particle column technology for polymer SEC (Waters ACQUITYTM Advanced Polymer Chromatography, APC) is applied as the SEC dimension in D1 or D2 in SEC X LC or LC X SEC configurations, respectively. With the small total column volume and superior plate number, such columns help reduce the total analysis time and improve resolution. The addition of multi-angle light scattering (MALS) to APC separations aids in the understanding of the polymer separations under higher shear in sub-3 micron particle columns. This information provides critical guidance for flow rate optimization for high molecular weight polymers. Aiming to improve the peak capacity and increase throughput on the LC dimension, this work also evaluates the use of sub-2 micron particle columns using ultra high-pressure liquid chromatography (UHPLC). Using narrow polystyrene standards with molecular weights ranging from 5 kg/mol to -1,000 kg/mol, we compared the chromatograms generated from the use of columns packed with 10, 5, 3.5, and 1.7 µm particles. The peaks are shown to get narrower as particle sizes become smaller when other parameters remain constant, indicating interaction-based polymer separations, similar to small molecule separations, benefit from reduced particle size. In conclusion, ultra high pressure 2D-LC (UHPLCxAPC) utilizing small particle size columns show the potential to significantly improve efficiency of polymer separations and shorten the runtime of 2D-LC, making this technique a practical tool for industrial use.

Characterization of synthetic polymers using ultra-high pressure two-dimensional liquid chromatography

254th National Meeting (2017)

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