Ultrasensitive Determination of Vitamin B₁₂ Using Disposable Graphite Screen‐Printed Electrodes and Anodic Adsorptive Voltammetry

Abstract

A facile, rapid and ultra‐sensitive method for the determination of vitamin B12 (cyanocobalamin) at the sub‐nanomolar concentration range by using low‐cost, disposable graphite screen‐printed electrodes is described. The method is based on the cathodic preconcentration of square planar vitamin B12s, as occurred due to the electro reduction of Co(III) center in vitamin B12a to Co(I), at −1.3 V versus Ag/AgCl/3 M KCl for 40 s. Then, an anodic square wave scan was applied and the height of the peak appeared at ca. −0.73 V versus Ag/AgCl/3 M KCl, due to the oxidation of Co(I) to Co(II) in the adsorbed molecule, was related to the concentration of the vitamin B12 in the sample. EDTA was found to serve as a key‐component of the electrolyte by eliminating the background signal caused by metal cations impurities contained in the electrolyte (0.1 M phosphate buffer in 0.1 M KCl, pH 3). It also blocks trace metals contained in real samples, thus eliminating their interference effect. The method was optimized to various working parameters and under the selected conditions the calibration curve was linear over the range 1×10−10–8×10−9 mol L−1 vitamin B12 (R2=0.994), while the limit of detection for a signal‐to‐noise ratio of 3 (7×10−11 mol L−1 vitamin B12) is the lowest value of any reported in the literature for the electrochemical determination of vitamin B12. The sensors were successfully applied to the determination of vitamin B12 in pharmaceutical products.

Recent Advances in the Fabrication and Application of Screen-Printed Electrochemical (Bio)Sensors Based on Carbon Materials for Biomedical, Agri-Food and Environmental Analyses

“…Accumulation of vitamin B 12 was achieved through the reduction of Co(III) to Co(I) which was pre-concentrated onto the surface of the electrode [60]. This was followed by the stripping step, whereby Co(I) was reoxidised to Co(II), which produced the analytical response.…”

Development of an electrochemical DNA biosensor for the detection of vitamin B12 (cyanocobalamin) at a carbon paste modified electrode with a manganese(II) complex

“…On the other hand, the reported detection limits on references [27], [28], and [32] are lower that of the proposed biosensor. In spite of their advantages arising from low detection limits, generally modified electrodes are made of expensive materials like gold nanotubes [31] or screen printed electrodes [32]. Also these nanomaterials or screen printed electrodes have complex synthesis processes and electrode preparation is very difficult [27,31,32].…”

“…In addition, the detection limit of the proposed methodology, comprising the modified CPE with (A) and dsDNA, is lower than that of the unmodified CPE [27]. On the other hand, the reported detection limits on references [27], [28], and [32] are lower that of the proposed biosensor. In spite of their advantages arising from low detection limits, generally modified electrodes are made of expensive materials like gold nanotubes [31] or screen printed electrodes [32].…”

“…In spite of their advantages arising from low detection limits, generally modified electrodes are made of expensive materials like gold nanotubes [31] or screen printed electrodes [32]. Also these nanomaterials or screen printed electrodes have complex synthesis processes and electrode preparation is very difficult [27,31,32]. However, Mn-dsDNA-CPE has very simple preparation procedure.…”

“…On the other hand, voltammetric methods are highly sensitive and rather accurate, do not require expensive instrumentation, and are rather frequently used to determine group B vitamins and therefore B 12 . Electrochemical techniques like cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV) and amperometry have been employed to the determination of B 12 [24][25][26][27][28][29][30][31][32][33][34]. Furthermore, chemical modifiers of electrode surfaces, particularly manganese complexes, give to the newly resulted electrodes excellent properties and can be utilized to the detection of B 12 [35][36][37][38][39].…”