Development of Sulfolane Modified Electrode Sensor for the Determination of Vitamin-B6, Vitamin-C and Uric acid

Abstract

Vitamin-B6 (VB6) and Vitamin-C (VC) are important biomolecules and are widely used as food additives or antioxidants and for the treatment of anemia, depression, acute seizures, scurvy, cold problems etc. Uric acid (UA) is the primary end product of purine metabolism. UA also coexists with VB6 and VC in biological fluids such as blood and urine. In this study, a simple and sensitive modified electrode sensor has been developed using Sulfolane (SFL) as a trifunctional electrochemical sensor for the determination of VB6, VC and UA. Cyclic voltammetry (CV), Differential pulse voltammetry (DPV) and UV-Visible spectroscopy were performed as detection techniques. In this work, glassy carbon (GC), gold (Au) and platinum (Pt) electrodes were used as the working electrode. The electrodes were modified with SFL by applying continuous potential cycle for 15 scans at a range of -1.0 to 2.0 V at 100 mV s-1. Then the electrodes were activated in phosphate buffer solution (PBS) (pH 7) by applying continuous potential cycle for 5 scans at a range of -0.5 V to 1.2 V. A ternary solution of VB6, VC and UA was prepared and the CV and DPV were taken at the modified (GC, Au and Pt) electrodes. It is seen that the performance of modified GC electrode is better than the modified Au and Pt electrodes. The influence of pH has been studied by varying pH from 3 to 9. The detection was mostly favorable at pH 7. The effect of different scan rates has been discussed and the variation of peak current was plotted with square root of scan rate. The peak current increases with the increase of square root of scan rates. The nearly proportionality of the peak current suggests that the peak current of the reactant at each redox reaction is controlled by diffusion process with some chemical complications. The effect of bare and modified GC electrode on single, binary and ternary solution of VB6, VC and UA have been studied. CVs of the single solution of VC, UA and VB6 at bare GC electrode shows the oxidation peaks at 0.34 V, 0.35 V and 0.74 V respectively. But at modified GC electrode VC, UA and VB6 gives the oxidation peaks at 0.15 V, 0.33V and 0.72 V respectively. At bare GC electrode, the ternary mixture of VC, UA and VB6 shows two oxidation peaks at 0.5 V and 0.74 V. But SFL modified GC electrode shows three separated and well defined oxidation peaks at 0.18 V, 0.34 V and 0.79 V respectively. The peak intensity of SFL modified electrode was high compared with the bare GC electrode. Similar behavior have been seen in the DPV technique. Quantitative analysis of VB6, VC and UA have been carried out by DPV using SFL modified GC electrode in a single, binary and ternary solution. In every case, the peak currents of VB6, VC and UA increased linearly with increasing their concentrations over the range of 0.5-2.5mM. The SFL modified GC electrode showed good selectivity and strong anti-interference activity for the determination of VB6, VC and UA in binary and ternary mixture with excellent results. The limit of detection (LoD) has been calculated by signal-to-noise ratio (S/N=3). For the simultaneous concentration change, the LoD for VB6, VC and UA at SFL modified GC electrode are 0.8 μML-1, 1.0 μML-1 and 0.2 μML-1 respectively. The sensitivity of VB6, VC and UA are 41.84 μA/mM/cm2, 31.12 μA/mM/cm2 and 138.14 μA/mM/cm2 respectively at SFL modified GC electrode. The practical application of the SFL modified electrode sensor was demonstrated by the determination of VB6 and VC in pharmaceutical tablet samples and UA in blood sample. The results have been valided by UV-Vis spectroscopic method and pathological method. The amount of VB6 and VC in some well-established pharmaceutical (Beximco, ACI, Square, Aristopharma, Opsonin, ACME etc) tablet samples have been found approximately same with compared to the labeled value. The single determination of VB6, VC and UA in tablet and blood samples by SFL modified GC electrode is very consistent with the determination of VB6, VC and UA by UV-Vis spectroscopic method and pathological method in the same samples. Thus it is suggested that the SFL modified sensor may be used in the pharmaceutical industry and pathology for the determination of VB6, VC and UA.