Impurity Analysis of Highly-Polar Compounds Without Using Ion-Pair Reagents

Introduction

Ion-pair chromatography can sometimes provide effective separation of highly-polar compounds that display almost no column retention in the reversed- phase mode. Ion-pair reagents which contain fluorine are often used for LC/MS; however, as ion-pair reagents tend to accumulate in the column, interface, switching to another separation mode may take a considerable amount of time to allow complete flushing of the residual ion-pair reagents. Here we introduce analytical conditions that do not include the use of an ion-pair reagent. Using a multi-mode ion- exchange column, a mobile phase consisting only of an aqueous solution of acetic acid and acetate was used. Aminoglycoside antibiotics, compounds that are typically separated by ion-pair chromatography, consist of several sugars and amino sugars. As these compounds display almost no optical absorption, but are easily ionized due to the amino group, a mass spectrometer is the most useful instrument for detection of these compounds.

December 17, 2010 GMT