Surface and kinetic effects in gas chromatographic studies of polystyrene

Abstract

GREGORY J. COURVAL and DEREK G . GRAY. Can. J. Chem. 54, 3496 (1976). Considerable variation in the measurement of polynier-solvent interactions using gc retention data may occur due to kinetic factors, surface excess concentrations of probe vapour, and nonlinear partition isotherms. The kinetic factors. which appear as a flow rate dependence of the retention volume. are anal) sed in terms of a previously reported theoretical model for retention on polymeric stationary phases passing through the glass transition. The predicted linear extrapolations to zero flow rate are obtained for the retention of tz-tetradecane on polystyrene. The variation of this flow rate dependence with temperature and with the thicknesc of the stationary phase are also in qualitative agreement with the theory. A simplified model for the effect of loading on the retention diagram is presented. Non-linear absorption and bulk sorption isotherms result in a dependence of retention volume on sample size, necessitating an extrapolation of the measured retention volumes to zero peak height. The temperature variation of the flow rate dependence, the effect of loading. and the effect of sample size on retention volume are all further complicated by uneven distribution of polymer on suplsort. From scanning electron micrographs of the beads it is evident that 'beading up' of the polystyrene on the glass surface may occur at low loadings, resulting in a non-uniform coating with large areas of the beads uncoated. It is concluded that in order to obtain reliable dava on polymer-solvent interactions using gas chromatography, all of the above-mentioned factors must be coniidered. Chem. 54, 3496 (1976). 11 peut se produire de grandes variations dans les rnesures des interactions polymkre-solvant en se basant sur des donnees de retention en cpg: ces variations proviennent de facteurs cinetiques, de concentrations d'excks au niveau de la surfaces et d'isothernies de partition nonlineaires. On analqse les facteurs cinetiques, qui apparaissent par une dependance des volumes de retention sur les vitesses d'ecoulernent, en termes du modi-ie thiorique rapport6 anterieurenient pour la retention sur des phases stationnaires sous forme de polymkre passant h travers une transition de verre. Comme prevu, on obtient des extrapolations lineaires sur une vitesse d'Ccoulement de r i r o pour la retention de 11-tttradCcane sur du poljst!,rkne. La variation de la vitesse d'Ccoulement avec la temperature et avec i'epaisseur de la phase stationnaire est aussi en accord qualitatif avec la theorie. On presente un modkle simplifii de 19efTet du chargement sur le diagramme de retention. Les isothernies nonlineaires d'absorption et de sorbtion de masse conduisent i une dipendance du v o l~~m e de retention sur la grosseur de l'echantillon et ceci necessite une extrapolation des volumes de retention niesurCs vers Line valeur nulle pour la hauteur des pics. De plus la \ariation avec la temperature dc la dependance de la vitesse d'icoulement ainsi que I'effet du chargenient et I'ei...

Solute diffusion in polymers. 1. The use of capillary column inverse gas chromatography

“…V°= 273.2tf/7>p (39) where Vg°i s the specific retention volume, T is the column temperature, and pp is the density of the polymer. The infinite dilution activity coefficient is related to the specific retention volume by the following:3…”

“…Others thickness in a packed column is usually large enough to guarantee that bulk properties are measured. 39 The issue remains unresolved.…”

Migration of Indirect, Food Additives: A Physical Chemical Approach

“…However, in studies of this type, it may be possible to generate retention data corresponding to equilibrium conditions by optimization of flow rate, temperature, and column particle size (Courval and Gray, 1976). Data obtained under such conditions may ultimately be rationalized in terms of infinite-dilution properties (weight fraction activity coefficient, fi2") and the related thermodynamic functions for selected polymer-solute systems (Patterson et al, 197 1).…”

Models for the migration of additives in polyolefins

“…Scanning electron microscopy studies of solution coated polystyrene films used in IGC experiments have shown that the film thickness can be highly (34) non-uniform at both low and high loadings .…”