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Organic Chemistry, Compound Detection 467

FIGURE 6

two ways. Indirect separation is based on the formation
of diastereomeric derivatives with covalent bonds between
the solute and an optically active reagent before chromato-
graphic separation. The second approach, direct separa-
tion, is based on the formation of labile diastereomeric
complexes with a chiral complexing agent (selector) in
the stationary or mobile phase.
Some of the applications of the chiral stationary phases
are for the determination of the enantiomeric purity in
product control, confirmation of an asymmetric synthe-
sis, and analysis of enantiomers found in biological fluids
FIGURE 5 Effect of chiral eluant on the separation of D- and such as urine and blood. LC has been used to separate
L-amino acid enantiomers by ligand-exchange chromatography. enantiomers in the milligram to gram scale. NMR spec-
troscopy using shift reagents has been used successfully in
the determination of enantiomeric natural products such
H. Chiral Separations by HPLC as monoterpenes.
The recent developments in chiral separations by GC and
LC has intensified the studies of asymmetrical (chiral) VI. GAS CHROMATOGRAPHY
molecules in several scientific disciplines, such as biol-
ogy, biochemistry, chemistry, and geochronology. Chiral
A. Derivatization Gas Chromatography
separations are of great interest in pharmacology and phar-
maceutical sciences because enantiomers can have differ- Conversion of sample compounds into volatile derivatives
ent pharmacological and toxicological effects in humans. make it possible to separate and analyze by GC, groups
Different bioactivities have also been discovered for enan- of compounds for which GC analysis would otherwise
tiomericpesticides,insecticides,andherbicides.Thechro- be impossible, e.g., amino acids, sugars, prostaglandins,
matographic separation of enatiomers can be achieved in and related compounds. The presence of different polar