Development of Diethylamine Modified Electrode for the Determination of Paracetamol, Tramadol and Uric acid

Abstract

Paracetamol (PA) and Tramadol (TD) are very important drugs for the treatment of common diseases such as cold, fever, headache etc. They are co-exist in some tablets. Uric acid (UA) is the primary end product of purine metabolism. UA also exists in biological fluids such as blood and urine. A modified electrode has been developed using diethylamine (DEA) as a trifunctional electrochemical sensor for simultaneous detection of UA, PA and TD. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and UVVis. spectroscopy were used 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 DEA by applying continuous potential cycle for 15 scans at a range of -0.5 to 1.5 V. Then the electrodes were activated in phosphate buffer solution (PBS) (pH 7) by applying continuous potential cycle for 10 scans at a range of -0.5 V to 1.5 V. A ternary solution of UA, PA and TD 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 is mostly favorable at pH 7. The effect of different scan rates has been discussed and the variation of peak current plotted against square root of scan rate. The peak currents increase proportionally with increasing square root of scan rates indicates the electrochemical processes are controlled by diffusion process. The effects of bare and modified GC electrode on single, binary and ternary solution of UA, PA and TD have been studied. CVs of the single solution of UA, PA and TD at bare GC electrode shows the oxidation peaks at 0.34V, 0.46V and 0.94V respectively. But at modified GC electrode it shows the oxidation peaks at 0.27V, 0.38V and 0.81V. At bare GC electrode, the ternary mixture of UA, PA and TD shows two oxidation peaks at 0.41V and 0.93V. But DEA modified GC electrode shows three separated and well defined oxidation peaks at 0.27V, 0.38V and 0.81V. The peak intensity of DEA modified electrodes are higher compared with the bare GC electrode. Similar behavior have been observed in the DPV technique. Quantitative analysis of UA, PA and TD have been carried out by DPV using DEA modified GC electrode in a single, binary and ternary solution. In every case, the peak currents of UA, PA and TD increase linearly with increasing their concentrations over the range of 0.5-2.5 mM. The DEA modified GC electrode shows good selectivity and strong anti-interference activity for the determination of UA, PA and TD in binary and ternary mixture with excellent results. The limit of detection (LoD) has been calculated by signalto-noise (S/N=3) ratio. In simultaneous detection, the LoD for UA, PA and TD are 1.95 μmol L-1, 1.45 μmol L-1 and 1.26 μmol L-1 respectively at DEA modified GC electrode. The sensitivity of UA, PA and TD are 52.08 μA/mM/cm2, 62.25 μA/mM/cm2 and 33.67 μA/mM/cm2 respectively at DEA modified GC electrode. DEA modified GC electrode has been successfully used for the quantitative determination of UA, PA and TD in some commercial tablets of different pharmaceutical companies of Bangladesh and biological fluids. The results have been valided by UV-Vis spectroscopic method and pathological report. The amount of PA and TD in some well-established pharmaceutical (Beximco, ACI, Square, Incepta, ACME etc) tablet samples have been found approximately same with compared to the labeled value. But the amount of PA, TD have been found less with compared to the labeled value in the tablets of some pharmaceutical companies (Opsonin, Renata, General, etc). Simultaneous detection of UA, PA and TD is not possible by UV-Vis spectroscopic method due to their very close absorbance maxima. The single determination of PA, TD and UA in tablet and blood samples by DEA modified GC electrode is very consistent with the determination of PA, TD and UA by UV-Vis spectroscopic method and pathological method in the same samples. Thus it is suggested that the DEA modified sensor may be used in the pharmaceutical industry and pathology for the determination of PA, TD and UA.