Viscosity detectors chromatography, refractive

Advances in size-exclusion chromatography, coupled with refractive index, absorption, viscosity, and lightscattering detectors, and MALDI-ToFMS, have made it possible to accurately determine molecular weight distribution (oligomer profiling), even at the relatively low values of polymeric additives (up to about 5000 Da). Advances in column design, e.g. high-resolution PS/DVB columns (> 105 plates m-1) mean that SEC can provide a valuable alternative to conventional HPLC techniques for the separation of small molecules. 

Size-exclusion chromatography (SEC) has become the technique of choice in measuring the molar-mass distributions of polymers that are soluble in easily handled solvents (Dawkins, 1989). The technique as widely practised is not an absolute method and a typical SEC system must be calibrated using chemically identical polymers of known molar mass with a narrow distribution unless a combined detector system (viscosity, light scattering and refractive index) is employed. 

Analysis and Characterization. Gas chromatography was performed with a Hewlett-Packard model 5880A equipped with capillary columns and a flame-ionization detector. Gel permeation chromatography was performed with a Hewlett-Packard HPLG model 1090A with a refractive index detector. Tacticity determinations were conducted with an F-19 nuclear magnetic resonance (NMR) spectrophotometer (Varian XL-100) at 94.12 MHz for triad analyses (13). Inherent viscosity measurements were performed in 2-butanone at 25.0 °C. 

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