Microscale chromatography has found numerous applications in liquid chromatography. The combination of enhanced-fluidity liquid mobile phases with packed-capillary LC is evaluated for polymer characterization using size-exclusion chromatography (SEC) and liquid chromatography at the critical condition (LCCC) phase. Separations of polystyrene polymers and copolymers are completed using liquid chromatography at the critical condition. The critical conditions of polystyrene polymers were approached by changing the concentration of CO(2) in the mixture combined with temperature and pressure variation. Because the solvent strength of enhanced-fluidity liquid mixtures is affected by temperature and pressure variation, the solvent strength could be fine-tuned to accurately find the critical condition. Long packed capillaries could be used in this application because the enhanced-fluidity mobile phases have low viscosities. High efficiencies resulted. The performance of packed-capillary and analytical-scale analytical columns containing the same packing material was compared for a challenging separation at the critical condition.

Abstract:The complete characterization of polymers requires the evaluation of both the molecular weight and chemical composition distributions. Size exclusion Ž . chromatography and liquid chromatography at the critical condition LCCC are two methods often used to obtain these distributions. Recently, matrix-assisted Ž . Ž . laser desorption ionization MALDI ᎐time of flight TOF mass spectrometry has been used for polymer characterization. The application of packed capillary SEC Ž . and LCCC is illustrated here for the characterization of poly propylene glycol based materials. Especially in the case of critical chromatography, packed capillary chromatography separations were achieved that were not possible using analyticalscale critical chromatography. In addition, the off-line combination of packedcapillary SEC and LCCC with MALDI-TOF is described.

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