Pyrolysis-gas chromatography-mass spectrometry for studying N-vinyl-2-pyrrolidone-co-vinyl acetate copolymers and their dissolution behaviour

Anal Chim Acta. 2011 Nov 14;706(2):305-11. doi: 10.1016/j.aca.2011.05.052. Epub 2011 Jul 19.

Abstract

Knowledge on the solubility behaviour and dissolution rate of speciality and commodity polymers is very important for the use of such materials in high-tech applications. We have developed methods for the quantification and characterization of dissolved copolymers of N-vinyl-2-pyrrolidone (VP) and vinyl acetate (VA) during dissolution in water. The methods are based on pyrolysis (Py) performed in a programmed-temperature vaporization injector with subsequent identification and quantification of the components in the pyrolysate using capillary gas chromatography-mass spectrometry (GC-MS). By injecting large volumes and applying cryo-focussing at the top of the column, low detection limits could be achieved. The monomer ratio was found to have the greatest effect on the dissolution rate of the PVP-co-VA copolymers. The material with the highest amount of VA (50%) dissolves significantly slower than the other grades. Size-exclusion chromatography (SEC) and Py-GC-MS were used to measure molecular weights and average chemical compositions, respectively. Combined off-line SEC//Py-GC-MS was used to determine the copolymer composition (VP/VA ratio), as a function of the molecular weight for the pure polymers. In the dissolution experiments, a constant VP/VA ratio across the dissolution curve was observed for all copolymers analysed. This suggests a random distribution of the two monomers over the molecules.

MeSH terms

  • Chromatography, Gel
  • Gas Chromatography-Mass Spectrometry / methods*
  • Kinetics
  • Molecular Weight
  • Pyrrolidines / chemistry*
  • Pyrrolidines / isolation & purification
  • Temperature
  • Vinyl Compounds / chemistry*
  • Vinyl Compounds / isolation & purification
  • Water / chemistry

Substances

  • Pyrrolidines
  • Vinyl Compounds
  • poly(vinylpyrrolidone-co-vinyl-acetate)
  • Water