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.