Improving Gas Chromatography–Mass Spectrometry Analysis of Essential Oils by Multivariate Curve Resolution: Full Identification of Co-eluting Compounds of Dracocephalum moldavica L

Methods such as gas chromatography coupled with mass spectrometry (GC–MS) are crucial for identification compounds of essential oils. This is a necessity when analyzing highly complex samples; all overlapped signals must be resolved and identified with high confidence. In this study, gas chromatography–mass spectrometry (GC–MS) combined with iterative resolution methods was used to characterize the essential oil components of Iranian Dracocephalum moldavica L. ( D. moldavica ). Due to the medicinal importance of D. moldavica , full identification of the components was performed using for the first time multivariate curve resolution-alternative least squares (MCR-ALS) as an auxiliary means to the analysis overlapping peaks. The analysis of GC–MS data revealed that 47 components exist in the D. moldavica essential oil and a total of 40 components were identified by direct similarity searches. However, with the help of MCR and different chemometric methods, the numbers of all resolved components were extended to 63 and a total of 54 components were identified by reversed matching with reference spectra. Major constituents in D. moldavica were neral (22.10%), geraniol (5.28%), E -citral (30.40%), neryl acetate (2.68%), and geranyl acetate (29.59%). The results proved that combining MCR techniques with GC–MS produces a powerful tool for the analysis of complex samples.