Amino acids separation stationary phase

A number of packings with different stationary phases have been tested for the GC separation of TFA-butyl esters of amino acids. Polyester stationary phases, e.g., 1%... 

A few years later, Blaschke designed purely synthetic chiral stationary phases obtained by emulsion polymerization of acrylamides prepared from amino acids [17]. These phases had been developed for preparative purposes and proved to be very efficient for the preparative resolution of various chiral drugs for which the enantiomers have been isolated for the first time. These earher applications include the separation of the enantiomers of the sadly well-known drug thalidomide (Fig. 6.2) [18],... 

In recent years, much effort has been devoted to developing methods for the separation of enantiomers by gas or liquid chromatography. - Two approaches have been used. One is based on forming derivatives of the analyte with an optically active reagent that forms a pair of di-astcreomers that can be separated on an achiral column. Ilic alternative method is to use a chiral liquid as the stationary phase. A number of amino acid -derived chiral phases have been developed for this purpose, and others are becoming available commercially. 

The above chemical separations work on the basis of forming diastereomeric pairs as intermediates the same principle applies to the column chromatography techniques that have been developed over the past few years, in which a chiral metal complex is attached to the stationary phase. A number of complexes based on Cu", Ni", Zn" and Co " have been shown to be capable of resolving amino acids. A reverse-phase technique has also been described in which Cu" or Zn" peptide complexes are used in the mobile rather than the stationary phase. ... 

Proteias, amino acids bonded through peptide linkages to form macromolecular biopolymers, used as chiral stationary phases for hplc iaclude bovine and human semm albumin, a -acid glycoproteia, ovomucoid, avidin, and ceUobiohydrolase. The bovine semm albumin column is marketed under the name Resolvosil and can be obtained from Phenomenex. The human semm albumin column can be obtained from Alltech Associates, Advanced Separation Technologies, Inc., and J. T. Baker. The a -acid glycoproteia and ceUobiohydrolase can be obtained from Advanced Separation Technologies, Inc. or J. T. Baker, Inc. 

Diamide Chiral Separations. The first chiral stationary phase for gas chromatography was reported by GH-Av and co-workers in 1966 (113) and was based on A/-trifluoroacetyl (A/-TFA) L-isoleucine lauryl ester coated on an inert packing material. It was used to resolve the tritiuoroacetylated derivatives of amino acids. Related chiral selectors used by other workers included -dodecanoyl-L-valine-/-butylamide and... 

Among various types of chiral stationary phases, the host-guest type of chiral crown ether is able to separate most amino acids completely (58). 

Erank H, G. J. Nicholson and E. Bayer, Rapid gas cliromatographic separation of amino acid enantiomers with a novel cliiral stationary phase , J. Chromatogr. Sci. 15 174-176(1977). 

The first partial chiral resolution reported in CCC dates from 1982 [120]. The separation of the two enantiomers of norephedrine was partially achieved, in almost 4 days, using (/ ,/ )-di-5-nonyltartrate as a chiral selector in the organic stationary phase. In 1984, the complete resolution of d,l-isoleucine was described, with N-dodecyl-L-proline as a selector in a two-phase buffered n-butanol/water system containing a copper (II) salt, in approximately 2 days [121]. A few partial resolutions of amino acids and dmg enantiomers with proteic selectors were also published [122, 123]. 

A pair of amino acids is separated in a column in which the stationary phase is saturated with water and the carrier solvent is methanol, CH,OH. The more polar the acid, the more strongly it is adsorbed by the stationary phase. The amino acids that were separated in this column are (a) HOOCCHNH2CH,COOH and (b) HOOCCHNH2CH(CH,)2. Which amino acid would you expect to be eluted first Explain your reasoning. Refer to Major Technique 4 on chromatography, which follows these exercises. 

A further thirty years were to pass before Kuhn and his co-workers (3) successfully repeated Tswetf s original work and separated lutein and xanthine from a plant extract. Nevertheless, despite the success of Kuhn et al and the validation of Tswett s experiments, the new technique attracted little interest and progress continued to be slow and desultory. In 1941 Martin and Synge (4) introduced liquid-liquid chromatography by supporting the stationary phase, in this case water, on silica in the form of a packed bed and used it to separate some acetyl amino acids. 

There is a wide variety of commercially available chiral stationary phases and mobile phase additives.32 34 Preparative scale separations have been performed on the gram scale.32 Many stationary phases are based on chiral polymers such as cellulose or methacrylate, proteins such as human serum albumin or acid glycoprotein, Pirkle-type phases (often based on amino acids), or cyclodextrins. A typical application of a Pirkle phase column was the use of a N-(3,5-dinitrobenzyl)-a-amino phosphonate to synthesize several functionalized chiral stationary phases to separate enantiomers of... 

Membranes offer a format for interaction of an analyte with a stationary phase alternative to the familiar column. For certain kinds of separations, particularly preparative separations involving strong adsorption, the membrane format is extremely useful. A 5 x 4 mm hollow-fiber membrane layered with the protein bovine serum albumin was used for the chiral separation of the amino acid tryptophan, with a separation factor of up to 6.6.62 Diethey-laminoethyl-derivatized membrane disks were used for high-speed ion exchange separations of oligonucleotides.63 Sulfonated membranes were used for peptide separations, and reversed-phase separations of peptides, steroids, and aromatic hydrocarbons were accomplished on C18-derivatized membranes. 

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