Determination of tocopherols and tocotrienols in cereals by pressurized liquid extraction-liquid chromatography-mass spectrometry.

A rapid analytical method including pressurized liquid extraction (PLE) and liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) has been developed for the determination of tocopherols and tocotrienols in cereals. The pressurized liquid extraction parameters were optimized in order to maximize the extraction efficiency. The use of methanol as extraction solvent at a temperature of 50 degrees C and a pressure of 110 bar, using one cycle of extraction with a static time of 5 min, provided the best results. A good LC separation was achieved using a C(18) column and a solution of 6.0 mM ammonia in methanol/water (97:3, v/v) as the mobile phase at a flow rate of 0.2 mL min(-1). MS coupling with an ESI interface in the negative ion mode was used as the detection technique. In the present work, it is shown that the addition of a base to the mobile phase is required to enhance the ionization of tocopherols and tocotrienols in negative ion mode electrospray ionization. The applicability of the method to cereal samples was confirmed. The reproducibility of the procedure was good, with relative standard deviations in the 6-10% range. The recoveries of added tocopherols from cereal samples ranged from 91 to 109%.