Method development for determination of total vitamin K using screen-printed graphene electrode

Abstract

In this work, a new method based on square-wave anodic stripping voltammetry (SWASV) technique using screen-printed graphene electrode was developed for a highly sensitive determination of trace total vitamin K (VK) in dietary supplement. The determination using SWASV consists of two steps. First is accumulation step at more negative potential constantly to preconcentrate and to change the substance from quinone to hydroquinone. For second step, the potential was scanned towards the positive direction for oxidation analysis. To enhance sensitivity, the various experimental parameters such as pH of electrolyte solution, accumulation potential, accumulation time, frequency, step potential, and amplitude were studied. Under the optimal conditions, the relationship between oxidative currents and concentrations of VK was linearity in the range of 1 to 15 µg mL-1 with a correlation coefficient of 0.9904 and limit of detection of 0.099 µg mL-1. Furthermore, the relative standard deviation for three concentrations of VK at 5, 10, and 15 µg mL-1 were 3.29, 3.18 and 3.16 (n=10), respectively. To evaluate efficiency of the proposed method, it was applied for the determination of total vitamin K in some dietary supplements with satisfactory recovery data in the range of 90.1 – 108.1%. The results obtained were in good agreement compared to standard method. The RSD was acceptable in the range of 1.7 to 6.9%. Such high sensitivity and reproducibility, therefore, the proposed method can be used as an alternative method for quality control of VK in dietary supplement.