Second-order calibration for the determination of fatty acids in pomegranate seeds by vortex-assisted extraction-dispersive liquid–liquid micro-extraction and gas chromatography-mass spectrometry
Multivariate curve resolution-alternating least squares (MCR-ALS) as a second-order calibration algorithm was proposed for the simultaneous analysis of eighteen fatty acid methyl esters (FAMEs) in a standard mixture and pomegranate seed sample using vortex-assisted extraction-dispersive liquid–liquid microextraction (VAE-DLLME), followed by gas chromatography-mass spectrometry (GC-MS). The chemometric resolution, identification and quantification of the target FAMEs in the standard mixture and real sample (i.e., the pomegranate seed) were carried out successfully in the presence of some uncalibrated interferences. The lack of fit (LOF) and reverse match factor (RMF) were used for the evaluation of the MCR-ALS results of the calibration samples. The LOF (%) and RMF values were in the ranges of 7.24–24.36 and 708–977, respectively. In addition, the regression coefficients (R2) and relative errors (REs, %) of the calibration curves of different FAs were in the satisfactory range of 0.9934–0.9989 and 3.70–7.45, respectively. The application of the proposed strategy to the pomegranate seed extract showed that linoleic acid, oleic acid, palmitic acid, stearic acid and cis-11-eicosenoic acid were the main fatty acids in the pomegranate seed with concentrations of 9098.0, 4873.0, 3147.0, 1960.0 and 1019.0 mg kg−1, respectively, and relative standard deviations (RSD, %) between 0.15 and 11.57. It is concluded that MCR-ALS combined with VAE-DLLME-GC-MS is a fast and simple strategy for the qualitative and quantitative analysis of complex samples such as natural products.