Medium Resolution ~1H-NMR at 62 MHz as a New Chemically Sensitive Online Detector for Size-Exclusion Chromatography (SEC-NMR)

摘要

A state-of-the-art, medium-resolution 1H-NMR spectrometer (62 MHz) is used as a chemically sensitive online detector for size-exclusion chromatography of polymers such as polymethylmethacrylate (PMMA) and polystyrene (PS). The method uses protonated eluents and works at typical chromatographic conditions with trace amounts of analytes (<0.5 g L~(-1) after separation). Strong solvent suppression, e.g., by a factor of 500, is achieved by means of T_1-filtering and mathematical subtraction methods. Substantial improvements are made with respect to previous work in terms of the sensitivity (signal-to-noise ratio up to 130:1, PMMA OCH_3) and selectivity (peak width, full width half maximum (FWHM) 4 Hz on-flow). Typical homopolymers and a blend are investigated to deformulate their composition along the dimensions of molecular weight and NMR chemical shift. These results validate this new hyphenated chromatography method, which can greatly facilitate analysis and is much more effective than previously published results.