Amino acids, acetylated, chromatographic separation

Direct and indirect chromatographic methods were developed and compared in systematic examinations for the enantioseparation of P-amino acids direct separation of underivatized analytes involved the use of commercially available Crownpak CR(-I-), teicoplanin, and ristocetin A CSPs [148], while indirect separation was based on precolumn derivatization with 2,3,4,6-tetra-G-acetyl-f)-D-glucopyranosyl isothiocyanate (GITC) or A - a-(2,4-dinitro-5-fluorophenyl)-L-alaninamide (EDAA, Marfey s reagent), with subsequent separation on a nonenantioselective column. 

Cimbura and Kofoed (50),mentioned earlier, used GLC to separate amphetamine and methamphetamine after acetylation with acetic anhydride in methanol. Derivatives were extracted using diethyl ether and chromatographed op columns of either 3% OV-17, OV-1, or SE-30. Column temperature was 160°C. They also reported the chromatographic determination of acetylated morphine on 3% SE-30, OV-1, or OV-17 at temperatures of 220°C. Cruickshank et al.(21) separated 21 amino acids as their trifluoroacetylated methyl esters. The column was 5% neopentyl glycol succinate on Gas Chrom P. Column temperatures were both isothermal and programmed 65°C for 20 min at 1.5°C/min then 2°C/min until 42.5 min then 4°C/min until 60 min then isothermal until about 75 min (see Figure 12.2). Chang et al. (19), used BSA/pyridine to form the TMS derivatives of levodopa, methyldopa, tyrosine. 

MM2 calculations, and the separation factors and capacity ratios, measured during isocratic elution, were related to the energy value changes between an analyte and a model phase. Diastereomers have very different stereostructures. The contact surface area with bonded allg l groups affects the elution order. Amino acids were derivatized with a chiral derivatization reagent, such as o-phthalaldehyde-AT-acetyl-L-cysteine (ref. 11) and N-tert-butylthiocarbonyl-L-cysteine, prior to the chromatographic analysis. 

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