Adsorptive Stripping Analysis of Riboflavin at Electrically Heated Graphite Cylindrical Electrodes

Electrically heated graphite cylindrical electrodes (HGCEs) made from ground pencil leads have been used to perform adsorptive stripping square wave voltammetry (SWV) measurements of trace riboflavin (RF). The SWV stripping peak current was significantly enhanced with increasing the electrode temperature only during preconcentration step. This enhancement was due to the forced thermal convection induced by heating the electrode rather than the bulk solution. It is the thermal convection that has the ability to improve mass transfer and facilitate adsorption thus enhance stripping responses. It was found that the detection limit of 5×10−9 M (S/N=3) could be obtained at an electrode temperature of 72 °C during 5 min accumulation, more than one magnitude lower than that at 22 °C (room temperature), the sensitivity could be enhanced ca. eight or four folds for two different RF concentration ranges. So it is possible to develop a new highly sensitive method to determine riboflavin at HGCEs. Such HGCEs were also successfully used to determine RF in multivitamin tablets.