ADDITION OF MODIFIER IN SUPERCRITICAL-FLUID CHROMATOGRAPHY USING A MICROBORE RECIPROCATING PUMP

Solubilities of polar analytes in supercritical CO2 can be enhanced by the addition of polar modifiers. The addition of modifier into an SFC system using a low cost reciprocating pump has been studied. Two different mixing chambers were evaluated for mixing the supercritical CO2 with modifier. It appeared that a mixing chamber with a packed bed was enough to reduce baseline noise from the modifier pump. Results from the effect of pressure and temperature with various modifier now rates were obtained. High percentages of modifier (> 15%) at a low CO2 pressure (2000 psi) caused baseline instability. In addition, different I.D. columns were tested with the system and the effect of modifier compressibility on detector noise was also studied. Several pharmaceutical compounds were separated to demonstrate system performance.