LC/UV/MS-MRM for the simultaneous determination of water-soluble vitamins in multi-vitamin dietary supplements

The purpose of this study was to optimize chromatographic and detection conditions for the simultaneous determination of water-soluble vitamins in multi-vitamin dietary supplements using a single chromatographic run. An approach using liquid chromatography with diode array and/or mass spectrometry for quantitation of seven B-complex vitamins [thiamine (B(1)), riboflavin (B(2)), nicotinamide (B(3)), pyridoxine (B(6)) pyridoxine, biotin, pantothenic acid, and folic acid] in multi-vitamin/multi-mineral daily supplements is described. This approach utilizes a reversed phase C18 column (4 mum; i.d.: 250x2.0 mm) with a gradient mobile elution profile, performed at a flow rate of 0.25 ml/min. After a 5-min isocratic elution at 100% A (0.1% formic acid in water), a linear gradient to 50% A and 50% B (0.1% formic acid in acetonitrile) at 15 min and then to 5% A and 95% B at 17 min was employed. Detection was performed with a photodiode array detector (DAD) in sequence with a triple-quad mass spectrometer in the multiple reaction mode (MS-MRM). Although good chromatographic separation of ascorbic acid was also obtained in extracts from multi-vitamin/multi-mineral supplements, the ascorbic acid could not be quantified properly due to rapid oxidation catalyzed by the minerals. This method was initially applied to determine water-soluble vitamins in representative multi-vitamin/multi-mineral tablets following the extraction of ground samples with a phosphate buffer (10 mM, pH 2.5). For multi-vitamin supplement tablets, this approach does not require any sample clean-up/pre-concentration steps except for centrifugation and filtration of the extract.