Multi-Analyte Sensor Based on Pencil Graphite Electrode for Riboflavin and Pyridoxine Determination

Riboflavin (VB 2 ) and pyridoxine (VB 6 ) are two of the eight water-soluble B vitamins that play an essential role and are correlated in normal function of the body. In the present study, cyclic voltammetry demonstrated that in Britton-Robinson buffer (pH 5.00) VB 2 undergoes a quasi-reversible electron transfer reaction and the oxidation of VB 6 is irreversible, both electrochemical systems being diffusion controlled at the pencil graphite electrode (PGE) surface. Also, a sensitive and selective voltammetric procedure has been developed for the simultaneous determination of the two compounds using PGE and square wave voltammetry (SWV). Two well-defined oxidation peaks with a voltammetric separation of more than 1.10 V were obtained in Britton-Robinson buffer (pH 5.00). The SWV curves exhibited linear responses with riboflavin and pyridoxine concentrations. Thus, for VB 2 two linear concentration ranges of 1.00 · 10 −7 –5.00 · 10 −5 M and 5.00 · 10 −5 –7.50 · 10 −4 M were obtained and in the case of VB 6 the linear response was between 2.50 · 10 −5 M and 2.50 · 10 −3 M. The detection limits for VB 2 and VB 6 were 7.38 · 10 −8 M and 1.10 · 10 −5 M, respectively. The applicability of PGE was successfully proved for simultaneous determination of VB 2 and VB 6 in pharmaceutical tablets with good accuracy and precision.