Determination of fatty acids in vegetable oils by GC-MS, using multiple-ion quantification (MIQ)

Multi-energy calibration (MEC) fundamentals, developed for atomic spectrometry, were adapted in this work to determine fatty acids in vegetable oils by gas chromatography-mass spectrometry. The procedure was denoted GC-MS-MIQ, where MIQ stands for multiple-ion quantification. Transesterification reaction was accomplished and two chromatographic runs per sample were carried out, similar as in one-point standard addition. Four m/z values for each FAME were selected and linear regression was computed relating intensities of each ion in the spiked and non-spiked sample. The slope of the obtained function was used to perform quantification, based on the concentration of standard added to the sample. Results obtained for two reference materials using GC-MS-MIQ were in good agreement with those provided by external calibration and were consistent with the certified values. Eleven edible vegetable oils from Mexican market were analyzed. Based on the obtained results, GC-MS-MIQ is prompted as a feasible alternative to perform multi-component quantitative analyses avoiding external calibration and ensuring the same chemical environment for the analyte and the calibrator.