Reactivation of an amino bonded phase liquid chromatographic column

Abstract

Amino-bonded phase liquid chromatographic columns can be used both in the normal and reversed phase mode for oil fractionation. However, the Schiff's base formation by amine-carbonyl condensation occurs during the chromatograhy and results in decreased recovery of the solutes unless the oil sample is first extracted to remove polar constituents possibly containing aldehyde or ketone moieties. Results of studies undertaken to reactivate columns after deactivation either by samples or by mobile phase carbonyls are cited. During conversion from one mode to the other - cyclohexane (normal phase) to methanol/water (reversed phase), acetone was inadvertently used as an intermediate polarity solvent resulting in extensive on column Schiff's base reaction. This deactivation of the column with acetone resulted in decreased retention of naphthalene (63%), anthracene (56%), and pyrene (49%); and the poorer column efficiency was evidenced in a 23% decrease in the number of effective theoretical plates. However, after reactivation by treatment with cyclohexane, both retention and column values returned to nearly original values. (BLM)