A simple strategy for d/l-carnitine analysis in food samples using ion mobility spectrometry and theoretical calculations

Abstract

This work presents a straightforward approach to the separation d/l-carnitine (d/l-Carn) using ion mobility-mass spectrometry (IM-MS) and theoretical calculations. Natamycin (Nat) was used as separation reagent to interact with the Carn, metal ions (G) were employed as ligand, the resultant ternary complexes [d/l-Carn + Nat + G]⁺ were observed experimentally. IM-MS results revealed that d/l-Carn could be baseline separated via complex formation using Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺, with a maximum peak separation resolution (R_p-p) of 2.91; Theoretical calculations were performed to determine the optimal conformations of [d/l-Carn + Nat + Li/K]⁺, and the predicted collisional cross section values were consistent with the experimental values. Conformational analysis was used to elucidate the enantiomeric separation of d/l-Carn at the molecular level via the formation of ternary complexes. Furthermore, quantitative analyses for the determination of the enantiomers were established with effective linearity and acceptable sensitivity. Finally, the proposed method was successfully applied in the determination of d/l-Carn in food samples.

Keywords: Diastereomeric complex; Food sample; Ion mobility–mass spectrometry; Separation and analysis; Theoretical calculation; l-/d-Carn.