Simultaneous detection of tocopherols, carotenoids, and chlorophylls in vegetable oils by direct injection C30 RP-HPLC with coulometric electrochemical array detection

Detection and quantification of tocopherols, carotenoids, and chlorophylls in vegetable oil have been used to aid their authentication. Their importance in influencing the oxidative stability of vegetable oils and their possible health benefits have been shown in numerous studies. Therefore, the need for a rapid and reliable analysis method has become increasingly important. This study demonstrates the application of C-30 RP-NPLC with electrochemical detection for the simultaneous analysis of tocopherols, carotenoids, and chlorophylls in vegetable oils. Aliquots of vegetable oils were dissolved in appropriate solvents and injected directly without saponification, thus preventing sample loss or component degradation. Effective separation of tocopherols, carotenoids, and chlorophylls was achieved. Detection was performed using a coulometric electrochemical array detector set between 200 and 620 mV. For a 25-muL injection, the respective detection limits for carotenoids, tocopherols, and chlorophylls were 1 fmol, 0.15 pmol, and 0.5 pmol, representing 1000-, 25-, and 5-fold enhancement over the UV-vis methodology. The detector response was linear between 0.01 and 2.00 mug/mL for all compounds studied. Within-day variations (CV) were between 2.0 and 6.3%, whereas between-day variations were between 2.7 and 7.4%. This method can be applied for rapid and sensitive analysis in the study of oil quality and adulteration.