Determination of betaines in vegetable oils by capillary electrophoresis tandem mass spectrometry. Application to the detection of olive oil adulteration with seed oils.

Abstract

A capillary electrophoresis-tandem mass spectrometry methodology enabling the simultaneous determination of betaines (glycine betaine, trigonelline, proline betaine and total content of carnitines) in vegetable oils was developed. Betaines were derivatized with butanol previous to their baseline separation in 10 min using a 0.1 M formic acid buffer at pH 2.0. Ion trap conditions were optimized in order to maximize selectivity and sensitivity. Analytical characteristics of the proposed method were established by evaluating its selectivity, linearity, precision (RSDs ranged from 4.8% to 10.7% for corrected peak areas), accuracy by means of recovery studies (from 80% to 99%) and LODs and LOQs at 0.1 ppb level. The method was applied to the determination of the selected betaines in seed oils and extra virgin olive oils. MS2 experiments provided the fingerprint fragmentation for all betaines studied in seed oils. In extra virgin olive oils, carnitines were not detected being possible to propose them as a feasible novel marker for the detection of adulterations of olive oils. Application of the developed method to the analysis of different mixtures of extra virgin olive oil with seed oil (between 2-10 %) enabled the detection and quantitation of the total content of carnitines. The results obtained show the high potential of the developed method for the authentication and quality control of olive oils.