Analysis of menthol optical isomers in tobacco products
Menthol can exist in four enantiomeric pairs, each of which has D-type and L-type separately. Different menthol isomers possess different sensory properties. The establishment of configuration analysis technology for the menthol isomer is of great value for the quality evaluation and application of menthol in tobacco. Based on the detailed study of the separation efficiency of eight menthol optical isomers by different non-chiral and chiral capillary columns, a method for separating eight menthol optical isomers from tobacco products by tandem chiral capillary columns and gas chromatography-mass spectrometry was established. The eight menthol optical isomers were successfully separated by CycloSil-B + BGB-175 tandem chiral capillary column. The chromatographic peaks of eight menthol optical isomers all met the separation requirements, and the shapes of all peaks were sharp and symmetrical. The response value and retention time had good interday stability, and the stationary phase loss was small under separation conditions, which had no significant influence on menthol detection. The limit of quantification (LOQ) of the established method was lower than 72.9 µg/L with the recoveries ranged from 92.1 % to 109.5 % at three spiked levels. The method was successfully applied to the separation and quantitative detection of menthol optical isomers in traditional cigarettes and heated cigarettes. The results showed that the dominant form of menthol in the tested samples was L-menthol, and traces of other menthol isomers were detected in most samples as well.