[Determination of trace vitamin B2 by fluorimetry after aqueous two-phase extraction based on acetone and ethanol]

Small molecular water-miscible organic solvent, such as ethanol, acetone and acetonitrile, can be used to form aqueous two-phase system for extraction of analytes in the presence of salts. Just based on it, the acetone-salt-H2O and the ethanol-salt-H2O systems were developed for the determination of trace vitamin B2 coupled with fluorimetry after aqueous two-phase extraction. Various factors including the type and amount of salts and organic solvents, extraction time, coexistent substance, and pH were studied. The experimental results show that the extraction efficiencies of vitamin B2 in the acetone-salt-H2O and the ethanol-salt-H2O system were 97.6%-98.4% and 94.2%-95.5%, respectively, in one-step extraction. Under the optimal conditions, these two extraction techniques gave linear dynamic ranges of 1.5 x 10(-7)-3.5 x 10(-6) mol x L(-1) and 2..0 x 10(-7)-1.5 x 10(-6) mol x L(-1), with detection limits of 0.031 and 0.041 microg, respectively. Both techniques were applied directly to determination of vitamin B2 in pharmaceutical tablets and injections with satisfactory results. The relative errors were--1.8%-1.1% as compared with China pharmacopoeia and the relative standard deviations were 1.5%-2.2% for vitamin B2 in the above samples. Compared with conventional liquid-liquid extraction or solid-phase extraction, these methods have outstanding advantages such as simple operation, high extraction efficiency, little interference with analytes and low toxicity.