Chromatographic Methods for Determination of Antimicrobial Agents in Fluids and Tissues

Abstract

Chromatography is a process which is used for separating complex mixtures based on their distribution between a mobile gas or liquid phase and a stationary liquid or solid phase. In liquid chromatography, a mobile liquid phase interacts with the sample molecules and with the stationary phase. “Reverse-phase” chromatography exists when a nonpolar stationary phase and a polar mobile phase are used. This type of liquid chromatography is especially useful in the clinical laboratory since a large variety of compounds of various weights and polarities in aqueous samples can be introduced directly into the chromatograph and separated on a single column by varying the composition of the mobile phase. The mobile phase is usually an aqueous buffer or a mixture of an organic solvent, such as methanol or acetonitrile, and water. An ion-pair reagent may be used with reverse- phase chromatography to modify the retention time of an ionic compound with an opposite charge. The most commonly used anionic ion-pair reagents are alkyl sulfonates (RSO3−), while quarternary amines are usually used as cationic ionic-pair reagents (Gerson and Anhalt 1980).