Semi-micro size-exclusion chromatography: Molecular-weight measurement of poly (ethylene terephthalate) and separation of oligomers and prepolymers

Summary Several polystyrene gels of different pore sizes were packed into a 500 mm×2.1 mm I.D. column. Semi-micro size-exclusion chromatography (SEC) using these columns was carried out with a system consisting of a triple piston pump, a micro loop injector and a flow cell with 1.0-μl cell volume constructed for semi-micro HPLC, because the dead volume of the injector and the cell volume of flow cell for conventional HPLC caused a significant loss in column efficiency. The effects of sample amount, injection volume and mobile phase flow rate on column efficiency and retention volume were examined and the optimized operational variables of the sample amount (below 500 μg), the injection volume (less than 15 μl) and the flow rate range (30–70 μl/min) determiend for semi-micro SEC. Oligostyrene, epoxy resin, phenol-formaldehyde resin and phthalates were analyzed by the optimized semi-micro SEC system under the given conditions. In addition, molecular weight distribution of four different poly(ethylene terephthalate) films was successfully measured by using a mixture of chloroform and hexafluoroisopropanol as the eluent.