Infrared detection of polymers in gel permeation chromatography

Abstract

Abstract A gel permeation chromatograph equipped with an on‐line Grubb‐Parsons infrared spectrometer is described. The versatility, specificity, sensitivity, and limitations of such an infrared detector are discussed with particular reference to spectrometer specification, eluent absorbance, and solute absorbance. A stable baseline is produced when this detector is operated at high temperatures, e.g., for the separation of polyethylene in o ‐dichlorobenzene at 135°C. Individual functional groups in a chemically inhomogeneous solute, such as a copolymer, may be monitored by repeated injections of the solute, changing the wavelength setting between separations. This procedure is illustrated with AB poly(styrene‐ b ‐ t ‐butyl methacrylate) block copolymer in trichloroethylene at 35°C.