FIELD: analytic chemistry, inversive-voltamperometric method of determination of water soluble vitamin B2 participating in redox reactions in living organism. SUBSTANCE: in agreement with method vitamin B2 is electrochemically concentrated on surface of graphite electrode with subsequent registration of anode voltampere curves. Method differs by concentration of vitamin B2 on glass-carbon (or pyrographic) electrode in the course of 60 to 120 s at electrolysis potentials (-0.5)-(-0.6) V against backgrounds of 0.05M KCI or in solution of 0.2M KCl in presence of hydrochloric or sulfuric acid or HClO4 with pH 2.0-4.0 with later registration of anode peaks under mode of fractional differentiation at rate of potential development of 10-20 mV/s. Concentration of vitamin B2 is determined by height of anode peak in potential interval from minus 0.18 to minus 0.30 V with reference to chlorine-silver electrode. EFFECT: improved authenticity. 2 tbl
