Automated Chiral Analysis of Amino Acids Based on Chiral Derivatization and Trapped Ion Mobility-Mass Spectrometry

A fast and fully automated method for chiral analysis has been developed by combining a chiral derivatization approach with high-resolution trapped ion mobility separation. Although the presented approach can be potentially applied to diverse types of chiral compounds, several benchmark amino acids were used as model compounds, focusing on the smallest amino acid alanine. An autosampler with an integrated chromatography system was used for inline chiral derivatization with (S)naproxen chloride and subsequent preseparation. Afterwards, derivatized amino acids were directly introduced into the electrospray interface of a trapped ion mobility-mass spectrometer for rapid diastereomer separation in the gas phase. This unique combination of preseparation and trapped ion mobility spectrometry separation in the negative ion mode enabled rapid chiral analysis within 3 min per sample. Furthermore, the diastereomer separation proved to be independent of alkali salts or other metal ions, offering robustness with regard to samples containing high amounts of salts. Highly sensitive detection of amino acid diastereomers was possible down to the lower nanomolar concentration range, and enantiomeric ratios could be readily determined from the recorded mobilograms with excellent reproducibility and precision. To demonstrate the general applicability of our method, alanine and other amino acids were analyzed from soy sauces and seasonings, which revealed extraordinarily high D-Ala contents of up to 99% in all samples.

Automated summary

A fast and fully automated method for chiral analysis has been developed by combining chiral derivatization with high-resolution trapped ion mobility separation. The method allows for rapid chiral analysis within 3 minutes per sample and is robust in samples containing high amounts of salts. Highly sensitive detection of amino acid diastereomers was possible down to the lower nanomolar concentration range, with excellent reproducibility and precision in determining enantiomeric ratios.