Stationary phases nomenclature

Vegvari, A., and Guttman, A. (2006). Theoretical and nomenclatural considerations of capillary electrochromatography with monolithic stationary phases. Electrophoresis 27, 716—725. 

The following conventions as to nomenclature will be adopted. The exchanging sorbable species are numbered 1,2,. . . , n in the sequence of decreasing affinity for the stationary phase. The number of species is n. Stationary- and mobile-phase concentrations t/i and Xi are so normalized that... 

The nature of the stationary phase can be incorporated in this nomenclature. The convention hereby is to denote the character of the stationary phase by inserting one or two letters in the middle. Hence, LSC and LLC are both forms of liquid chromatography (LC mobile phase is a liquid), while the stationary phase is a solid (S) and a liquid (L), respectively. 

The first reaction used for the modification of porous silica in chromatography involves an alcohol as the organic species. This process is referred to as an esterification reaction. This may seem like incorrect nomenclature in order to describe the chemical process taking place between the silianol (Si — OH) and the organic compound (R — OH). However, the OH of the silanol is an acidic species, so the reaction taking place involves an acid and an alcohol, which, in typical organic chemistry nomenclature, is an esterification. The chemical reaction is illustrated in Fig. 2. The product of this reaction can be used as a stationary phase in gas chromatography because the material is thermally stable up to temperatures of approximately 300°C. However, the Si — O — C bond that exists between the surface and the bonded moiety is hydrolytically unstable in the presence of relatively small amounts of water. Therefore, these materials... 

The various symbols appearing in the equation are defined in the nomenclature. The last term of the equation accounts for solute transfer between mobile and stationary phase. The driving force is the difference between the stationary phase concentration at equihbrium and the concentration at the interface. The rest of the terms arise from the standard continuity equation. The coefficient of the first term on the right-hand side is the dispersion coefficient in the mobile phase This model corresponds to the Fickian analogy where the dispersion coefficient is treated as a diffusion coefficient. 

The focus is on concepts in reversed-phase liquid chromatography (RPLC), though the same concepts are usually applicable to other modes of HPLC. International Union of Pure and Applied Chemistry (IUPAC)10 nomenclature is used. The term sample component is often used interchangeably with analyte and solute in the context of this book. As mentioned in Chapter 1, the most common stationary phase is a hydrophobic C18-bonded phase on a silica support used with a mixed organic and aqueous mobile phase. The terms packing and sorbent often refer to the bonded phase whereas solid support refers to the unbonded silica material. 

The development of high performance stationary phases for amino acid analysis has been vigorously pursued since the introduction of the first amino acid analyser (Spackman et al., 1950). The low UV extinction coefficient of most amino acids means that current detection methods depend upon the reaction of the primary amino group of the amino acid to yield a coloured or fluorescent derivative. The most popular reagents, referred to by their most common nomenclature, are the following ... 

A nonpolar mobile phase passing through a packed column that contains a polar stationary phase defines normal-phase HPLC (NP-HPLC). For example, if -hexane comprises the mobile-phase and silica gel is used for the stationary phase, separations of nonpolar organic analytes as shown in Fig. 4.1 is accomplished. With respect to neutral organic compounds, the polar and ionic domains cannot be reached by NP- HPLC. NP-HPLC was the first high-pressure form of liquid chromatography to be developed. If the stationary phase could be made hydrophobic by chemical treatment and the mobile phase made more polar, a reversal of mobile/stationary-phase polarities could be achieved. Like it or not, we are stuck with this nomenclature RP-HPLC has certainly extended the range of analyte polarity that... 

Nomenclature from distillation carried over to chromatography. We speak of a chromatography column as if it were divided into discrete sections (called theoretical plates) in which a solute molecule equilibrates between the mobile and stationary phases. Retention of a compound on a column can be described by the number of theoretical equilibration steps between injection and elution. The more equilibration steps (the more theoretical plates), the narrower the bandwidth when the compound emerges. 

Metal interaction chromatography is an HPLC technique that can separate many biopolymers because of their differential ability to form complexes with metal ions [1]. It employs a stationary phase with an appropriate metal immobilized via chelating functions bound to the surface. Retention and separation of the sample components occur largely by their interaction with the chelated metal. Although immobilized metal affinity chromatography (IMAC) is a common name for the technique, it is called metal interaction chromatography (MIC) in this book to conform to the nomenclature used for the other interactive chromatographic methods for biopolymer separation by HPLC. 

USP Nomenclature Code USP Stationary-Phase Description Similar Stationary Phases... 

Following the same nomenclature as in adsorption (since the fundamental phenomena for chromatography) is the same as adsorption, if Cs is the concentration of solute in stationary phase and C is the concentration in the mobile phase. Then the distribution coefficient between the two phases K = CsjC can be given by ... 

---