Chiral analysis amino acids

Amino acids (chiral analysis) Pentafluoracetic anhydride Heptafluorobutyryl anhydride Esterification with deuterium Nkoihara and... 

YP Belov, AY Aksinenko, B Blessington, AH Newman. Chiral aminophosphonate eluent for enantiomeric analysis of amino acids. Chirality 8 122-125, 1996. 

Derivatization of a racemic compound with an achiral group may play an important role in the analysis of a chiral compound (Fig. 7-15). In the case of substances with low or no UV-activity, the compounds can be rendered detectable by introducing an UV-absorbing or fluorescent group. If the racemate itself shows selectivity on a chiral stationary phase (CSP), this method can be applied to reduce the limit of detection. Examples have been reported in the literature, especially for the derivatization of amino acids which are difficult to detect using UV detection. Different derivatization strategies can be applied (Fig. 7-16). 

Nokihara K, Gerhardt J Development of an improved automated gas-chromatographic chiral analysis system application to non-natural amino acids and natural protein hydrolysates. Chirality 2001 13 431. 

Peptide synthesis from y9-amino acids is particularly attractive for first feasibility micro-reactor tests as there are no chiral centers which may complicate analysis of the products [5, 88]. y0-Peptides are also attractive owing to their stmctural and biological properties, especially concerning the stability versus degradation by peptidases as compared with their a-analogues (see original citations in [5]). 

Mass spectrometry (MS) is also being used to add another dimension of analysis to achiral-chiral analysis. Recently, an achiral-chiral column-switching LC/LC-MS/MS method was reported for the pindolol enantiomers in human serum (Motoyama et al., 2002) and phenprocoumon metabolites (Kammerer et al., 1998). For analytes that have very poor chromophores or cannot naturally fluoresce, MS detection can be more sensitive for the underivatized form of the analyte. Also, MS detection can be particularly useful when very similar analytes that differ in mass (such as some amino acids and metabolites) cannot be satisfactorily separated chromatographically,... 

S Weinstein, MH Engel, PE Hare. The enantiomeric analysis of a mixture of all common protein amino acids by high-performance liquid chromatography using a new chiral mobile phase. Anal Biochem 121, 370, 1982. 

An approach, similar to that employed in the analysis of tartrate mixtures, has been used for the chiral discrimination of amino acid (M/j/s) mixtures, using an amino acid of defined configuration as reference (S). The proton-bound trimers [S2-M H]+ form [S M H]+ and [S2H]+ fragments upon CID or MIKE decay (equations (9)-(12)). With two independent measurements of the fragmentation ratio [S-M-H] /[S2H] from either [S2-M -H] and [52-M5-H]" , the differences in binding energies can be determined. The relative gas phase basicities (GB) of the molecular pairs [S-M] and [S2] can be derived from equations (13) and (14). 

Petritis, K. et al., Simultaneous analysis of underivatized chiral amino acids by liquid chromatography—ionspray tandem mass spectrometry using a teicoplanin chiral stationary phase, J. Chromatogr. A, 913, 331, 2001. 

Yu, Y-R and Wu, W-H., Simultaneous analysis of enantiomeric composition of amino acids and A -acetyl-amino acids by enantioselective chromatography. Chirality, 13, 231, 2001. 

An experimental design approach was also used in Reference 26 for the chiral analysis of amino acid derivatives. The screening and optimization schedule followed... 

Perrin, C., Vargas, M.G, Vander Heyden, Y., Maftonh, M., Massarf D.L. Fast development of separation methods for the chiral analysis of amino acid derivatives using capillary electrophoresis and experimental designs. J. Chromatogr. A 2000, 883, 249-265. 

Amino acid enantiomers can be separated on a chiral stationary phase after derivatization with chloroformates (Abe et al., 1996). The derivatization procedure is quite simple and rapid, but the derivatizing reagent must be synthesized, which complicates the assay. Another method for the analysis of amino acid enantiomers uses N,0-pentafluoropropionyl isopropyl derivatives and a chiral column with NPD detection (Hashimoto et al., 1992). 

Abe I, Fujimoto N, Nishiyama T, Terada K, Nakahara T. 1996. Rapid analysis of amino acid enantiomers by chiral-phase capillary gas chromatography. J Chromatogr A 722 221. Ahuja S. 1976. Derivatization in gas chromatography. J Pharm Sci 65 163. 

Analysis using a CMPA is usually resolved on a nonchiral column. A transient diastereomeric complex is formed between the enantiomer and the chiral component in the mobile phase, similar to the complexes formed with chiral stationary phases. A review by Liu and Liu (2002) cites several papers where addition of CPMAs has been used in analyzing amphetamine-related compounds. Some CPMAs include amino acid enantiomers, metal ions, proteins, and cyclodextrins. Advantages of this method of analysis include the use of less expensive columns and more flexibility in the optimization of chiral separation (Misl anova and Hutta, 2003). 

CSPs and chiral mobile phase additives have also been used in the separation of amino acid enantiomers. Another technique that should be mentioned is an analysis system employing column-switching. D-and L- amino acids are first isolated as the racemic mixture by reverse-phase HPLC. The isolated fractions are introduced to a second column (a CSP or a mobile phase containing a chiral selector) for separation of enantiomers. Long et al. (2001) applied this technique to the determination of D- and L-Asp in cell culture medium, within cells and in rat blood. 

CE has been applied extensively for the separation of chiral compounds in chemical and pharmaceutical analysis.First chiral separations were reported by Gozel et al. who separated the enantiomers of some dansylated amino acids by using diastereomeric complex formation with Cu " -aspartame. Later, Tran et al. demonstrated that such a separation was also possible by derivatization of amino acids with L-Marfey s reagent. Nishi et al. were able to separate some chiral pharmaceutical compounds by using bile salts as chiral selectors and as micellar surfactants. However, it was not until Fanali first showed the utilization of cyclodextrins as chiral selectors that a boom in the number of applications was noted. Cyclodextrins are added to the buffer electrolyte and a chiral recognition may... 

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