UNI-MB - logo
UMNIK - logo
 
E-resources
Full text
Peer reviewed
  • Efficient enantioresolution...
    Varfaj, Ina; Protti, Michele; Di Michele, Alessandro; Macchioni, Alceo; Lindner, Wolfgang; Carotti, Andrea; Sardella, Roccaldo; Mercolini, Laura

    Analytica chimica acta, 10/2021, Volume: 1180
    Journal Article

    Single enantiomers of mandelic acid (1), 3-phenyllactic acid (2), and 3-(4-hydroxyphenyl)lactic acid (3) are the subject of many fields of investigation, spanning from the pharmaceutical synthesis to that of biocompatible and biodegradable polymers, while passing from the interest towards their antimicrobial activity to their role as biomarkers of particular pathological conditions or occupational exposures to specific xenobiotics. All above mentioned issues justify the need for accurate analytical methods enabling the correct determination of the individual enantiomers. So far, all the developed liquid chromatography (LC) methods were not or hardly compatible with mass spectrometry (MS) detection. In this paper, a commercially available Cinchona-alkaloid derivative zwitterionic chiral stationary phase that is, the CHIRALPAK® ZWIX(−) was successfully used to optimize the enantioresolution of compounds 1–3 under polar-ionic (PI) conditions with a mobile phase consisting of an acetonitrile/methanol 95/5 (v/v) mixture with 80 mM formic acid. With the optimized conditions, enantioseparation and enantioresolution values up to 1.46 and 4.41, respectively, were obtained. In order to assess the applicability of the optimized enantioselective chromatography conditions in real-life scenarios and on MS-based systems, a proof-of-concept application was efficiently carried out by analysing dry urine spot samples spiked with 1 by means of a LC-MS system. The (S)<(R) enantiomer elution order (EEO) was established for compounds 1 and 2 by analysing a pure enantiomeric standard of known configuration. This was not possible for 3 because not commercially available. For this compound, the same EEO was identified applying a procedure based on ab initio time-dependent density-functional theory simulations coupled to electronic circular dichroism analyses. Moreover, a molecular dynamics simulation unveiled the role of the phenolic OH in compound 3 in the retention mechanism. Display omitted •ZWIX(−) allows the enantioresolution of the three aromatic α-hydroxy acids.•The optimized polar-ionic conditions are fully compatible with MS detectors.•The developed LC method can be used to study biological matrices with MS detectors.•Combining in silico simulations and ECD analyses is useful to derive the EEO.•The retention mechanism can be explained with molecular dynamic simulations.