Electrochemical oxidation and electroanalytical determination of xylitol at a boron-doped diamond electrode

Xylitol is a reduced sugar with anticariogenic properties used by insulin-dependent diabetics, and which has attracted great attention of the pharmaceutical, cosmetics, food and dental industries. The detection of xylitol in different matrices is generally based on separation techniques. Alternatively, in this paper, the application of a boron-doped diamond (BDD) electrode allied to differing voltammetric techniques is presented to study the electrochemical behavior of xylitol, and to develop an analytical methodology for its determination in mouthwash. Xylitol undergoes two oxidation steps in an irreversible diffusion-controlled process (D=5.05×10–5 cm2 s–1). Differential pulse voltammetry studies revealed that the oxidation mechanism for peaks P1 (3.4≤pH≤8.0), and P2 (6.0≤pH≤9.0) involves transfer of 1 H+/1e−, and 1e− alone, respectively. The oxidation process P1 is mediated by the •OH generated at the BDD hydrogen-terminated surface. The maximum peak current was obtained at a pH of 7.0, and the electroanalytical method developed, (employing square wave voltammetry) yielded low detection (1.3×10–6 mol L–1), and quantification (4.5×10–6 mol L–1) limits, associated with good levels of repeatability (4.7%), and reproducibility (5.3%); thus demonstrating the viability of the methodology for detection of xylitol in biological samples containing low concentrations.