Soaps chromatography

The purity of the compound (e.g., the amount of mono-, di-, or trisul-fonated diphosphine) can be determined by HPLC using the technique called soap chromatography with a single-wavelength (254 nm) detector.2 Analytical separation was carried out on a 250 x 4.6 mm i.d. stainless-steel... 

The most common way to create an RP-IPC system is to use a genuine chemically bonded reversed phase column (e.g. C18 see section 3.2.2.1) and to use large pairing ions with a hydrophobic alkyl chain dissolved in the mobile phase. This technique was introduced by Knox and Laird, who named it soap chromatography [380]. Because of the usually long alkyl chains of the pairing ions, the use of Cl 8 phases is to be recommended in order to avoid effects that are related to the critical chain length (see section 3.2.2.1). 

Knox, J.H. and Laird, G.R. Soap chromatography a new high performance chromatographic technique for separation of ionizahle materials dyestuff intermediates. J. Chromatogr. 1976, 122, 17-34. 

Conventional IPC separations were achieved by adding organic amines and ammonium salts of varying chain lengths as cationic IPRs for anionic analytes and alkyl or aryl sulfonates and sulfates as anionic IPRs for cationic solutes. Since these IPRs exhibit good tensioactive properties, IPC was originally named soap chromatography [1]. 

Remarkable number of different names was introduced to these methods. The technique has been called soap chromatography [113], solventgenerated ion-exchange [114], ion-interaction [115], and ion-pair [116]. Researchers introduced a similar number of different theories for the description of the effect of ionic mobile-phase additives on the retention of charged analytes essentially, each specific name for this technique corresponds to its own distinct retention theory. Melander and Horvath [116] divided existing theories into two main groups stoichiometric [113,114,117-119] and nonsto-ichiometric [120-133]. 

J. H. Knox and G. R. Laird, Soap chromatography—a new high-performance liquid chromatographic technique for separation of ionizable materials Dyestuff intermediates,/. Chromatogr. 122 (1976), 17-34. 

This is, by far, the most commonly used form of reversed-phase IPC. This technique has been also called soap chromatography although, in soap chromatography, the use of detergents as counterions is introduced. 

Soon, Knox thought to use the hydrophobic effect to form ion-pairs in aqueous phases. He developed the first use of reversed-phase ion-pair chromatography in 1976 [6]. He termed it soap chromatography. He added ionic surfactants to the polar hydro-organic mobile phase. They adsorb on the alkyl-bonded stationary phase. They also associate with the hydrophobic and ionic analytes. 

J.H. 10X and G.L., Laird Soap Chromatography, A new HPLC Technique for Separation of lonizable Materials Dyestuff Intermediates, J. Chromatogr., 122 17 (1976). 

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