Determination of coenzyme Q10 and Q9 in vegetable oils

A new sensitive and selective method has been developed for the quantification of the total coenzyme Q9 (CoQ9) and coenzyme Q10 (CoQ10) concentration in vegetable oil samples. The coenzyme Q fraction is isolated by solid-phase extraction (SPE) on amino phase eluting with a mixture of heptane:ethyl ether. The organic solvent is evaporated under nitrogen, and the residue is dissolved in a mixture of acetonitrile:tetrahydrofuran and finally is analyzed by reverse-phase high-performance liquid chromatography with a mass detector. The sensitivity of the method is based on the high efficient formation of the radical anions [M (-.)] of CoQ9 and CoQ10 by negative atmospheric pressure ionization. Interferences are minimized by using mass detection of the [M (-.)] ions ( m/ z = 797.5 for CoQ9 and m/ z = 862.5 for CoQ10) in selective reaction monitoring mode ( m/ z = 797.5 --> m/ z = 779.5 and m/ z = 862.5 --> m/ z = 847.5) using a triple-quadrupole mass spectrometer. The method was successfully applied to sunflower, soybean, and rapeseed oils, with a limit of quantification of 0.025 mg/kg for both compounds.