Separation of Free Acids C2-C5 in Dilute Aqueous Solution Column Technology

Abstract

Free acids, C₂–C₅, are strongly adsorbed by the diatomite support, metal column tubing, metal on the inlet side of the chromatographic column as well as glass wool used as column plugs. Silanized supports and silanized glass wool are also unsatisfactory for use with free acids. Acid additives to the stationary phase are important for deactivation of both the support and metal column tubing. Phosphoric acid appears to be the most effective acid additive. Glass column tubing does not adsorb acids. Teflon is an inert support for acids, but cannot be used to prepare the highly efficient columns normally required. Low polarity stationary phases are effective in separation of the iso-butyric/propionic (iC₄/C₃) acid pair. These include the SP-1200 stationary phase and the Chromosorb 101 porous polymer.