Objective To establish a method of determining vitamin B12 in health food products by liquid chromatography electrospray ionization tandem mass spectrometry(LC-MS/MS).Methods After mixing samples with internal standard solution of ginsenoside Re,the mixtures of samples were extracted by solid phase extraction,and separated on a Bio Basic-18 PIONEER column(150 mm×2.1 mm,5 μm) by a mobile phase of methanol(A) + water(B) with the gradient elution program.Detection was carried out by a liquid chroma...