Efficient Enantioselective Separation And Determination Of Trace Impurities In Secondary Amino Acids (i.e., Imino Acids)

Abstract

An R-(-)-1-(1-naphthyl)ethyl carbamoylated-β-cyclodextrin bonded phase in conjunction with a nonaqueous polar mobile phase was used for the highly selective enantioseparation of a number of secondary amino acids after their pre-column derivatization with 9-fluorenylmethyl chloroformate (FMOC). Under the conditions employed, the FMOC reagent served to "lock" the imino acid into their existing conformation thereby preventing the possibility of racemization. Furthermore, it served to increase the sensitivity to the point that trace level enantiomeric impurities were easily detected. Compared with separations that use traditional reversed-phase solvents, this method showed several advantages: higher selectivity towards the imino acid enantiomers investigated, shorter analysis times, faster equilibration of the column, more stable baseline and more sensitive fluorescence detection. The detection limits for FMOC derivatives of proline, trans-4-hydroxyproline, cis-4-hydroxyproline, pyroglutamic acid, 3,4-dehydroproline, thiaproline, penicillamine acetone adduct and pipecolic acid are in the low femtomole range. The method was used for evaluation of enantioselectivity of a number of "optically pure" commercial imino acid standards. Enantiomeric impurities as low as 0.0001% (1 ppm) can be determined in some cases. High precision determination of trace levels of d-imino acids in the presence of large amounts of corresponding (opposite) l enantiomer at 1, 0.1, 0.01% and below are demonstrated. © 1992.

Department(s)

Chemistry

Comments

National Institute of General Medical Sciences, Grant R01GM036292

International Standard Serial Number (ISSN)

0021-9673

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2023 Elsevier, All rights reserved.

Publication Date

09 Oct 1992

PubMed ID

1452629

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