High-pressure liquid chromatography chiral

Once again, the ratio of diastereomers is the same as that of the original enantiomers. High-pressure liquid chromatography has been used in a similar manner and has wider applicability. The direct separation of enantiomers by gas or liquid chromatography on a chiral column has also been used to determine optical purity. " Other methods... 

Acid catalyzed hydrolysis followed by the identification of D-amino acids in the hydrolysate is equally useful. To make this possible the amino acids in the mixture are acylated with an enantiomerically pure amino acid, for instance with the N-carboxyanhydride of L-leucine. In the resulting mixture of dipeptides any racemized residue is revealed by the formation of two dipeptides that are diastereoisomers of each other, for instance L-leucyl-L-phenylalanine and L-leucyl-D-phenylalanine. Since these are compounds with different physical properties they are separable and appear as a doublet on recordings of an amino acid analzyer. In recent years the conversion to diastereoisomers became unnecessary because the availability of chiral supports now permits separation of enantiomers by high pressure liquid chromatography (HPLC) and also by thin layer chromatography on plates covered with a chiral layer. 

Brucine is used in a similar manner and the carboxyl unit of the amino acid is coordinated to the tertiary amine unit in brucine rather than the poorly basic amide nitrogen. Selective crystallization of these salts leads to their separation, and basic hydrolysis leads to an enantiopure amino acid. It is now possible to separate many racemic mixtures into their enantiomeric components by using high-pressure liquid chromatography (HPLC) fitted with a column that contains a chiral compound bound to an adsorbent (known as chiral HPLC columns). Such columns have been developed by William H. Pirkle (United States 1934-). The chiral HPLC column is prepared by coating a chiral chemical compound on an inert material when a solution of the racemic mixture passes through this column, one enantiomer is adsorbed to the column material better than the other. These are sometimes called Pirkle columns. 

They do not distinguish between the two isomers. Neither did the IOC testing procedures as used at the 2002 Winter Olympics. The optical isomers of methamphetamine can be separated (and distinguished) by high-pressure liquid chromatography (HPLC) using a chiral column. Baxter requested that the IOC test his urine samples to confirm which isomer was present, a request that was declined. 

The second Litaudon report described the methods required to separate each of the racemic compounds from the others as well as the specifications for a chiral high-pressure liquid chromatography (HPLQ method that separated some pairs of enantiomers. 

In addition to high-performance liquid chromatography (HPLC), the chiral resolution using CMPAs was also carried out by supercritical fluid chromatography (SFC) [91] and capillary electrochromatography (CEC) [92-98]. Salvador et al. [91] used dimethylated /1-cyclodextrin as the mobile phase additive on porous graphite carbon as the solid phase for the chiral resolution of tofizopam, warfarin, a benzoxazine derivative, lorazepam, flurbiprofen, temazepam, chlorthalidone, and methyl phehydantoin by SFC. The authors also studied the effect of the concentration of dimethylated /1-cyclodextrin, the concentration of the mobile phase, the nature of polar modifiers, outlet pressure, and the column temperature on the chiral resolution. 

A series of planar chiral pyridine-fused ferrocene analogs (366) have been prepared and the enantiomers are resolved by chiral High performance (pressure) liquid chromatography (HPLC) see High Performance Liquid... 

CSP = chiral stationary phase SMBC = simulated moving bed chromatography HPLC = high-performance liquid chromatography MPLC = medium pressure liquid chromatography SFC = super-critical fluid chromatography. 

De la Puente ML (2004) Highly sensitive and rapid normal-phase chiral screen using high-performance liquid chromatography-atmospheric pressure ionization tandem mass spectrometry (HPLC/MS). J Chromatogr A 1055 55-62... 

---