Design of Differential Pressure Detection System for Size Exclusion Chromatography and the Estimation of its Performance

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When a polymer solution passes through a capillary tubing, pressure difference between the inlet and the outlet of the capillary tubing is proportional to the viscosity of the polymer solution which changes with molecular weight as well as the concentration. A differential pressure detection system was designed and the system was applied to the polymer solution eluted from size exclusion chromatography (SEC) columns.To calculate molecular weight averages for polymers, a calibration curve of log RpxM vs retention volume was constructed using polystyrene (PS) samples. Here, Rp is the value of the differential pressure divided by the response of a differential refractometer (RI) and M is molecular weight. A correction procedure of the time lag of the response of RI was developed. To apply the calibration curve constructed with PS to polymers other than PS, response correction factors for these polymers were measured and molecular weight averages of these polymers were determined accurately.This system was also applied for the determination of molecular weight distributions and composition distributions for several copolymers.