Determination of Myo-inositol and d-chiro-inositol in black rice bran by capillary electrophoresis with electrochemical detection

A high-performance capillary electrophoresis (CE) method with electrochemical detection (ED) is developed for simultaneous determination of myo-inositol and d-chiro-inositol in black rice bran in this work. A 140 μm diameter copper-disk electrode operated in a wall-jet configuration, which exhibited good response at +0.65 V (relative to the saturated calomel electrode (SCE)) for the two analytes in 50 mm sodium hydroxide solution, was used as working electrode. The optimum conditions for determination was optimized with regard to the potential applied to the working electrode, concentration of the running buffer, separation voltage and injection time. The analytes were separated within 20 min. Excellent linearity was obtained in the concentration range from 1.0×10⁻⁶ to 1.0×10⁻⁴ g/ml for both analytes. The detection limit (S/N=3) was 5.3×10⁻⁷ and 7.3×10⁻⁷ g/ml for myo-inositol and d-chiro-inositol, respectively. The work provides a useful method for the analysis of myo-inositol and d-chiro-inositol in black rice bran.