Analytica Chimica Acta 706 (2011) 305–311 Contents lists available at ScienceDirect Analytica Chimica Acta j ourna l ho me page: www.elsevier.com/locate/aca Pyrolysis–gas chromatography–mass spectrometry for studying N-vinyl-2-pyrrolidone-co-vinyl acetate copolymers and their dissolution behaviour  Aleksandra Chojnacka a,b,∗ , Abdul Ghaffar a,c , Andrew Feilden d , Kevin Treacher e , Hans-Gerd Janssen a , Peter Schoenmakers a a Analytical-Chemistry Group, Van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands b Dutch Polymer Institute, P.O. Box 902, 5600 AX Eindhoven, The Netherlands c Department of Chemistry, University of Engineering and Technology, Lahore, Pakistan d AstraZeneca R&D CHARNWOOD Pharmaceutical Development, Bakewell Road, Loughborough, Leicestershire LE11 5RH, UK e AstraZeneca, R&D, Pharmaceutical Development, Macclesfield, Cheshire, SK10 2NA, UK a r t i c l e i n f o Article history: Received 1 March 2011 Received in revised form 24 May 2011 Accepted 27 May 2011 Available online 19 July 2011 Keywords: Copolymer dissolution Copolymer characterization Pyrolysis–GC–MS SEC N-vinyl-2-pyrrolidone Vinyl acetate a b s t r a c t 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. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The ever increasing number of applications of complex poly- meric materials causes a concomitant need for the development of new methods to connect polymer structure with mate- rial behaviour. One vital property may be polymer dissolution, especially when polymers are used for biomedical or pharma- ceutical applications. Typical examples are polymeric implants and controlled-release media for drug delivery. In the latter case, implantation under the skin, injection into the body and oral intake  Presented at the 5th International Symposium on the Separation and Charac- terization of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, 26–28 January, 2011. ∗ Corresponding author at: Analytical-Chemistry Group, Van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amster- dam, The Netherlands. Tel.: +31 20 525 8179. E-mail address: A.Chojnacka@uva.nl (A. Chojnacka). may be considered. For such uses of polymers, knowledge of the rates of dissolution and/or extraction is imperative. This is also the case in other applications of specialty or commodity polymers, for example when the polymer is used as a film-forming agent for hair-styling cosmetics, as food-packaging materials or for fuel lines in cars. Because polymers can be extremely complex mixtures of molecules of various sizes, chemical compositions, end groups, etc., and because subtle changes in the molecular structure may have a huge effect on the polymers’ behaviour, the development of mean- ingful structure–property relationships is a very challenging task. Polymer dissolution is typically studied by viscometry or by Fourier-transform infrared (FTIR) spectroscopy [1–4]. Zhang et al. [5] studied dissolution kinetics of polystyrene (PS) in biodiesel. Dis- solution was measured at different temperatures for PS reference materials of different molecular weights. Gravimetric analysis and FTIR microscopy were compared. FTIR showed better precision, lower detection limits and much shorter analysis times. More- over, gravimetry required greater samples than FTIR microscopy. Bonacucina et al. [6] used acoustic spectroscopy and viscosity 0003-2670/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2011.05.052