Acrylonitrile-butadiene-styrene (ABS) composite electrode for the simultaneous determination of vitamins B2 and B6 in pharmaceutical samples

A lab-made affordable composite electrode based on acrylonitrile-butadiene-styrene (ABS) and graphite was developed and applied for the simultaneous determination of vitamins B-2 (riboflavin, VB2) and B-6 (pyridoxine, VB6) in pharmaceutical samples. Different ABS-graphite composite electrodes (AGCE) were prepared in proportions ranging from 40 to 80% (graphite, m/m) and characterized by a many complimentary techniques such as thermogravimetry (TG), Raman spectroscopy, Fourier transform-infrared (FTIR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Differential pulse voltammetry (DPV) was employed for analytical purposes, being several parameters investigated to determine the optimum experimental conditions. Best performance was obtained using as electrolyte 0.1 mol L-1 acetate buffer solution (pH 4.0), with a pulse amplitude of 100 mV, a scan increment of 5 mV, a modulation of time of 0.05 s, and a time interval of 0.5 s, resulting in a scanning rate of 10 mV s(-1). The use of a 70% AGCE electrode under optimized conditions provided as linear responses for VB2 and VB6 intervals from 0.25 to 1.2 mu mol L-1 (r = 0.997), and from 25 to 454 mu mol L-1 (r = 0.989), respectively, with limits of detection of 0.15 mu mol L-1 for VB2 and 10 mu mol L-1 for VB6. The AGCE presented satisfactory results for the simultaneous determination of VB2 and VB6 in commercially available tablets, with recoveries between 99.5 and 98.0%, being those statistically compatible to those found by a reference spectrophotometric procedure.