STUDIES ON BASE-LINE STABILIZATION IN A M EASUREMENT BY SIZE-EXCLUSION CHROMATOGRAPHY

The best conditions for rapid baseline stabilization, a stable baselin e, and precise measurements of the retention volumes and average molec ular weight of polystyrene(PS) were studied. It was assumed that a sta ble baseline could be obtained by keeping the temperature difference b etween both sides of a refractive index(RI) detector cell, reference a nd sample, constant. Under this assumption, the best combination of th e temperatures of the column, RI cell, room, and mobile phase were exa mined. The adjustment of the temperatures of the column, mobile phase and RI cell to room temperature, for example 25 degrees C was the best for the stability of the baseline. This temperature condition made it possible to shorten the time to attain a stable baseline. The time re quired to stabilize the baseline was 40 minutes, and the baseline fluc tuation was 2.2 x 10(-7) RIU/h. The second appropriate condition was k eeping the temperatures of the column and RI at 40 degrees C and those of the room and the mobile phase at 25 degrees C. Adjusting the tempe ratures of the column and RI to room temperature tvas required if the temperature of the mobile phase was not controlled.