Analytical Sciences

Computational Prediction of Diastereomeric Separation Behavior of Fluorescent o-Phthalaldehyde Derivatives of Amino Acids

Kenichiro TODOROKI,* Tatsuki NAKANO,* Hiroki WATANABE,* Jun Zhe MIN,* Koichi INOUE,* Yoshinobu ISHIKAWA,** and Toshimasa TOYO’OKA*

*Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga, Shizuoka 422-8526, Japan
**Laboratory of Physical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga, Shizuoka 422-8526, Japan

We have developed a convenient method for predicting the LC resolution of amino acid diastereomers through computational calculations. For acquiring experimental data, we derivatized 10 amino acids using o-phthalaldehyde and N-acetyl-L-cysteine as fluorogenic diastereomer-forming reagents and analyzed the diastereomers using reversed-phase LC and fluorescence detection. For theoretical chemical calculations, we used the publicly available semi-empirical calculation software MOPAC2012. Using the obtained experimental and theoretical data, we determined the change in analytical resolution with differences in the structure of the diastereomers. From the results obtained, we concluded that greater conformational change through diastereomeric derivatization induced an increase in the contact area with the stationary phase, leading to higher resolution.

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