HIGHLY SENSITIVE AND SELECTIVE DETERMINATION OF RIBOFLAVIN BY FLOW-INJECTION ANALYSIS USING PARALLEL DUAL-CYLINDER MICROELECTRODES

A novel wall-jet cell with parallel dual cylinder (PDC) microelectrode s was constructed and used for flow injection analysis (FLA). The dete ctor takes the advantages of ''redox recycling'' between bipotentiosta ted microcylinder electrodes (- 0.4 V/SCE and 0.0 V/SCE respectively) and shows high sensitivity and selectivity for riboflavin which is ele ctrochemically reversible. In 0.1 mol 1(-1) NaHSO3 media and at a flow rate of 1.0 ml 1(-1), 56.8% collection efficiency was found at a PDC device with cylinder diameter of 20 mum and an interelectrode gap of 2 mum. With this device, the FIA peak current at collector electrode ha d a linear relationship with riboflavin concentration over a wide rang e (from 70 ng to 35 pg), and the detection limit was 35 pg (signal-to- noise ratio of 3). For 10 successive replicate injections of 35 ng and 3.5 ng of the analyte, relative standard deviations were 1.7% and 2.8 % respectively. This method was applied to the direct determination of riboflavin (vitamin B2) in multivitamin tablets without the usual liq uid chromatographic separation procedures and good results were obtain ed. The method proposed is simple, rapid and economic.