Reversed phase chromatographic theory

Several studies attempted to relate the partition coefficient P of a solute in a liquid chromatographic or a gas chromatographic system with the composition of the two phases, one of which has a varying composition [19-23]. Tijssen et al. [24] and Schoenmakers [25] derived a relation between the partition coefficient and a binary mobile phase in reversed-phase HPLC from the solubility parameter theory of Hildebrand et al. [26]. Similarly, a relation can be derived for liquid-liquid extraction with extraction liquids composed of three components ... 

In general, there is a wide variety of chromatographic modes (types) that can be employed for the HPLC determination of food components, but only a few have been used for the determination of NOC. These include partition/adsorption on silica gel, liquid-liquid partition on polar-bonded phase (e.g., cyano, amino) or nonpolar hydrophobic-bonded phase (e.g., reversed-phase), and anion-exchange chromatography. Macrae (61) discussed the theories behind the various modes of chromatography. 

In this article we will discuss the use of reversed-phase chromatography in the analysis of nucleic acid fragments. For in-depth reviews of chromatographic theory and general applications, the reader is referred to several reviews which are available (B24, B31, G5, K8, M16, S17, S23). 

In the past, several theoretical models were proposed for the description of the reversed-phase retention process. Some theories based on the detailed consideration of the analyte retention mechanism give a realistic physicochemical description of the chromatographic system, but are practically inapplicable for routine computer-assisted optimization or prediction due to then-complexity [9,10]. Others allow retention optimization and prediction within a narrow range of conditions and require extensive experimental data for the retention of model compounds at specified conditions [11]. 

CHROMATOGRAPHIC PLATE THEORY AND REVERSED-PHASE SOLID-PHASE EXTRACTION... 

Structure of Reversed-Phase Sorbents Reversed Phase as a Partitioning Mechanism Chromatographic Plate Theory and Reversed-Phase Solid-Phase Extraction... 

The cavity model of solvation provides the basis for a number of additional models used to explain retention in reversed-phase chromatography. The main approaches are represented by solvophobic theory [282-286] and lattice theories based on statistical thermodynamics [287-291]. To a lesser extent classical thermodynamics combining partition and displacement models [292] and the phenomenological model of solvent effects [293] have also been used. Compared with the solvation parameter model all these models are mathematically complex, and often require the input of system variables that are either unknown or difficult to calculate, particularly for polar compounds. For this reason, and because of a failure to provide a simple conceptual picture of the retention process in familiar chromatographic terms, these models have largely remained the province of the physical chemist. 

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