Aromatic acids reversed-phase liquid

The prediction of retention times in a given eluent from log P has been proposed for aromatic hydrocarbons.19 The log A values of phenols21 and nitrogen-containing compounds22 were also related to their logP, and the calculated log P was used for the qualitative analysis of urinary aromatic acids, i.e. for the identification of metabolites in urine from the differences of log P in reversed-phase liquid chromatography.23,24... 

The agreement between the observed and predicted k values of aromatic acids was within 10%. The correlation coefficient was 0.954 (n = 32). An error of greater than 10% for 3-hydroxy-2-naphthoic acid and 2-hydroxybenzoic acid was attributed mainly to an error in their K.A values.25 The partition coefficient, logP, and dissociation constant, pKA, of analytes can be obtained by simple calculations and by computational chemical calculations, and thus the retention time can be predicted in reversed-phase liquid chromatography. 

Jones, P. Wellington, C.A. Optimisation in chromatography Theory and application to the separation of aromatic acids in reversed-phase liquid chromatography. J. Chromatogr. 1981, 213, 357-361. 

Zhao, Q., Sannier, F., Garreau, I., Lecoeur, C., and Piot, J. M., Reversed-phase high-performance liquid chromatography coupled with second-order derivative spectroscopy for the quantitation of aromatic amino acids in peptides application to hemorphins, /. Chromatogr. A, 723, 35, 1996. 

Ion pairing agents in liquid-liquid systems in reversed-phase mode have included dihydrogenphos-phate for separation of tricyclic amines, octyl sulfate for catecholamines, and tetrabutylammonium for aromatic carboxylates and anions of sulfonamides, to exemplify some of the comparatively few applications. Liquid stationary phases coated on the alkyl-bonded phase include 1-pentanol, butyronitrile, and tributylphosphate. In normal-phase liquid-liquid ion pair chromatography aqueous perchlorate solution has been coated on to silica particles for ion pair separation of catecholamines and related compovmds and tetrabutylammonium ion at neutral pH for carboxylates and anions of sulfonamides. The organic mobile phase often contained dichloromethane and butanol. In the normal-phase mode on silica alternative separation systems have been described with aqueous perchloric acid in methanol added to dichloromethane as mobile phase for separation of amines such as drug substances. This is not an extensively utilized, but quite useful, kind of separation, which has been named ion pair adsorption chromatography. 

---