Polymer analysis by column liquid chromatography coupled semi-on-line with Fourier transform infrared spectrometry

Abstract

Additives in polymers were identified by solvent-elimination based coupling of reversed-phase column LC and FTIR spectrometry. A spray-jet interface was used to deposit the effluent from a narrow-bore LC column on a zinc selenide window. The deposited additives were analysed by FTIR transmission microscopy, yielding identification limits in the low-nanogram range. Good-quality IR spectra were obtained for components present in PVC and polypropylene samples. These spectra allowed the characterization of the additives by spectral library search and/or spectral interpretation. The usefulness of the spray-jet interface system for the coupling of size-exclusion chromatography (SEC) and FTIR spectrometry was examined on the basis of the analysis of a polystyrene standard mixture. Representative IR spectra of the SEC effluent indicate that the SEC–FTIR system can be used for the determination of compositional changes across the polymer molecular mass distribution.