Ligand-exchange chromatography of amino acids on copper-, cobalt- and zinc-chelex 100.

Procedures for the ligand-exchange chromatography of amino acids on copper-, cobalt-and zinc-Chelex 100 have been examined. Ligand exchange on the copper complex affords a simple and rapid method for the removal of amino acids (except for aspartic and glutamic acids) from dilute solutions. The influence of the pH on the binding of amino acids to the metal complex was also studied. The bound amino acids could be eluted with ammonium hydroxide which also causes a slight metal leakage. Chromatography on cobalt- and zinc-Chelex 100 showed that only the basic amino acids were quantitatively attached to these complexes at pH 8.3-9.5, whereas the others were predominantly EXCLUDED. This procedure can be used for the selective concentration and removal of basic amino acids in the presence of other amino acids.     

Ligand-exchange chromatography of amino sugars and amino acids on copper-loaded silylated controlled-pore glass

The application of silylated controlled-pore glass (CPG) particles as a stationary phase for the liquid chromatographic separation of selected amino acids and amino hexoses is reported. Copper-loaded columns prepared from CPG particles whose surface was silylated to immobilize an ethylenediamine functional group were employed. Copper bleeding from the column occurred but was compensated by 10^-4M copper in the ammoniacal eluent. Hydrolysis of the siloxane bonded to the surface limited the practical lifetime of a column to 50 h of continuous operation.     

Ligand-exchange chromatography of alkaloids.

Alkaloids are separated by liquid chromatography on resins having functional carboxyl groups combined with copper (II) ions. The eluent is aqueous alcohol containing ammonia. Some resins retain alkaloids much better than others. Alkaloids studied included morphine, codeine, strychnine, atropine, papaverine, narcotine, cocaine, quinine, cinchonine and methadone.     

Gas chromatography of amino acids.

This review summarizes all papers that have appeared on the gas chromatography of amino acids (including the iodoamino acids) and their enantiomers in the period 1956-mid-1974. It has been found that the methods used for analysis of amino acids can be divided into three classes: (1) degradative procedures and techniques for converting the amino acid into another chemical compound; (2) procedures based on esterification of the carboxyl group and derivatization of the a-amino and other reactive groups in at least two steps; and (3) procedures based on a simultaneous derivatization of the carboxyl and a-amino groups in one reaction medium. For the treatment of the amino acid or its alkyl ester, three approaches can be distinguished for the two latter cases, i.e., acylation, alkylation (including silylation) and condensation. Of the procedures used for the resolution of optical antipodes, two methods are discussed, namely analysis of diastereoisomers on optically inactive stationary phases and separation of enantiomers on optically active stationary phases.     

Quantitative gas-liquid chromatography of non-protein amino acids.

The quantitative gas--liquid chromatographic analysis of non-protein amino acids, in the presence of protein amino acids, is described. The amino acids were determined as their N-trifluoroacetyl n-butyl esters on an ethylene glycol adipate column. The relative molar responses of 38 amino acids are reported.     

Ligand-exchange chromatography of carbohydrates and glycoconjugates

The current status of ligand-exchange chromatography (LEC) is reviewed in the light of recent developments, especially regarding mobile phase conditions and choice of metal ions. Further, parameters governing selectivity are emphasized. The paper is divided into two parts: LEC at acidic/neutral pH and at alkaline pH. The general characteristics of each part are outlined and illustrated by appropriate applications, including bioanalysis of carbohydrates in complex mixtures. In particular, the exceptionally strong complexation between carbohydrates and certain metal ions at alkaline pH appears promising for enrichment and clean-up possibilities owing to the high degree of inherent selectivity. Finally, future directions are discussed with regard to the intricate isolation and separation problems associated with glycotechnology. Further advances within this field will depend on the development of analytical methodologies for minute amounts (femtomoles) of complex carbohydrate mixtures present on proteins, receptors and cell surfaces and inside the cells.     

Ligand-exchange chromatography of amino acid enantiomers and its application to the biotransformation of DL-aspartic acid byPseudomonas dacunhae

Summary The separation of the D and L enantiomers of eighteen essential α amino acids has been investigated by ligand-exchange chromatography (LEC). The effect of column temperature on the retention times and resolution of individual amino acid enantiomers has been studied by varying the temperature from 25 to 50 °C for a mobile phase containing Cu²⁺ ions. By use of a temperature of 50 °C and Zn²⁺ in the mobile phase, eight of the eighteen amino acid enantiomers can be resolved sufficiently well for practical application. Only phenylalamine, tyrosine, and tryptophan can be separated by use of Ni²⁺ as complexation metal at 50 °C. LEC has been used to monitor the decarboxylation of racemic DL-aspartic acid byPseudomonas dacunhae. Analysis of DL amino acid enantiomers in different media was performed at column temperatures of 30 and 50°C by addition of 0.125 mM Cu²⁺ to the aqueous mobile phase. It was found that the analytical performance is most dependent on the identity of the metal used for complexation; the concentration of the metal was of secondary importance and the column temperature less important still.     

Rapid determination of amino acids by high-performance liquid chromatography: release of amino acids by perfused rat liver.

Perfused rat liver can be considered as one of the most suitable ex vivo models for studies of liver metabolism. To assess the possible effect of L-carnitine and some of its acyl esters on proteolysis in the rat liver, the amino acid derivatization and high-performance liquid chromatographic separation of Tapuhi et al. [Anal. Biochem., 115 (1981) 123] was modified.