Single-pump on-line parallel addition of modifier for packed column supercritical fluid chromatography

Abstract

A single syringe pump is employed in this report to add modifier (methanol) through a parallel connection device, which can maintain a constant and lasting (at least 6 h) ratio of methanol without any contamination of the pump. The amount of methanol in supercritical CO₂ is measured by gas chromatography. Psoralen and isopsoralen are applied as examples to illustrate the elution effect. With a fixed modifier line, the longer the CO₂ line, the higher the concentration. Variations in pressure and/or temperature also have some influence upon the methanol ratio. The single-pump parallel device can conveniently alter the property and ratio of the modifier, and is a probable substitute for gradient programming performed by a dual-pump system.