Determination of rutin and other flavonoids by flow-injection/adsorptive stripping voltammetry using nujol-graphite and diphenylether-graphite paste electrodes.

The possibility of determination of twelve flavonoids (fisetin, galangin, hesperetin, hesperidin, kaempherol, morin, myricetin, naringin, quercetin, quercitrin, rutin, rhamnetin) using adsorptive stripping voltammetry in a flow injection system is examined. Carbon paste electrodes based on mixtures of nujol-graphite and diphenylether-graphite were used and compared as working electrodes and measurements were made using both 'direct' and 'medium-exchange' procedures. The effect of experimental parameters such as pH, accumulation potential and period, presence of various compounds was examined. Sample size (typically 0.33 ml) is greatly reduced by applying a reciprocating flow of the sample plug through the detector during the preconcentration step. The instrumental sensitivities and lower detection limits were calculated for all flavonoids in all cases. In some cases the differences are so high that determination of certain flavonoids in the presence of excess of others is allowed. Depending on the flavonoid, the electrode type, and the measurement procedure the analytical range and the reproducibility (RSD%) were 10(-5)-10(-8) M and 2.5-10%, respectively. A simple procedure is developed for the electrochemical determination of rutin in a multivitamin preparation.