Graphene oxide mixed carbon paste electrode was used to look into the electrochemical performance of bio-active drug, mefenamic acid using voltammetry technique. The outcome of effect of pH, accumulation time, concentrations, scan rate, and excipients were studied. Quantitative determination of mefenamic acid conceded using highly sensitive differential pulse voltammetric method. The detection limit was found to be 0.95 nM for the concentration range 7.0 x 10-7 M to 1.0 x 10-10 M. A possible equal number of electron and proton found mechanism of electrochemical oxidation of mefenamic acid was proposed, and activation parameters ΔH≠ = 26.56 kJ mol-1, ΔS≠ = -248.7J K-1 mol-1, Ea = 29.04 kJ mol-1 were determined.

Electrochemical analysis of bio-active drug nimesulide (NIM) has been examined at carbon paste electrode using modifiers graphene oxide and reduced form of graphene oxide modified (GO/CPE & rGO/CPE) by voltammetry techniques. Effect of various parameters pH, concentrations, varying scan rates, and interfering agents were considered. Linear relation between peak potential, peaks current, scan rate, temperature, heterogeneous constant, concentration variation was attained. Different voltammetric techniques were utilized to study the application part of the proposed sensors, such as differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The linear response was observed in the range of 300 to 0.1nM with a detection limit of 11.20 nM (DPV) 1.08 nM (SWV) at GO/CPE and 1.03 nM (DPV) and 0.1nM (SWV) at rGO/CPE. A probable mechanism of electrochemical oxidation of NIM was proposed, and activation parameters such as Ea = 21.12 kJ mol-1, ΔH≠ = 18.64 kJ mol-1, ΔS≠ = -299.7 J K-1mol-1 and ΔG≠= 70.67 kJ mol-1, were determined.

A novel electrochemical sensor for the determination of secretolytic agent ambroxol was constructed by electrochemical deposition of eriochrome black-T (EBT) on surface of carbon paste electrode (CPE). Different voltammetric techniques like cyclic voltammetry, linear sweep voltammetry and square wave voltammetry were used. Modified paste electrode was characterized by atomic force microscope (AFM). The voltammetry dependence on current, potential, pH, concentrations, scan rate, temperature and excipients were investigated in optimized experimental conditions. According to the liner relation between peak potential, peak current, scan rate, effect of temperature, heterogeneous rate constant ambroxol concentration, differential pulse voltammetric was used for the quantitative determination in phosphate buffer solution. The linear response was obtained in the range of with a detection limit LOD = 4.8 nM. The possible electrochemical oxidation of two electrons and two proton free radical mechanisms proposed and activation parameters of ambroxol were determined. Further, the sensor was successfully applied in pharmaceutical and biological fluid sample analysis.

Valacyclovir (VCH) is an antiviral drug, used in the management of viral infections such as herpes simplex and varicella-zoster in humans. It is rapidly converted to acyclovir which has antiviral activity against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) and Varicella-zoster virus (VZV) both in vitro and in vivo. Electrochemical behavior was studied using cyclic voltammetric method, and the analytical application was studied using differential pulse voltammetric technique. The process on the surface of electrode was found to be irreversible and diffusion controlled. The charge transfer coefficient, heterogeneous rate constant, the number of electron transferred and activation parameters were calculated. Possible free radical reaction mechanism taking place on the surface of electrode was proposed. Calibration plot constructed using differential pulse voltammetric technique and applied for quantitative analysis in pharmaceutical and human urine sample. Limit of detection (LOD) and limit of quantification (LOQ) were calculated and found to be 0.028 and 0.09 μM, respectively. The present work describes the electrochemical behavior of an antiviral drug, VCH and its determination in pharmaceutical samples. The method shows the development of a sensor for selective and sensitive determination of VCH.

The incredible progress in the application of organic molecule for the development of electrochemical sensor with superior sensitivity has witnessed in the last decade. Electro oxidation of bioactive molecule. ambroxol (ABL) has been investigated by Patton and Reeders modified carbon paste electrode (PR/CPE) using voltammetry techniques. Modified carbon paste electrode (CPE) characterized by atomic force microscope (AFM). The voltammetry dependence on current, potential, pH, concentrations, scan rate, temperature. According to a liner relation between peak potential, peak current, scan rate, effect of temperature, heterogeneous rate constant ambroxol concentration, square wave voltameter methods (SWV) used for the quantitative determination in phosphate buffer solution was developed. A linear response was obtained in the range of with a detection limit LOD = 2.5 nM. The possible electrochemical oxidation of two electrons and two protons free radical mechanism is proposed, and thermodynamic parameters of ambroxol oxidation were determined. The analytical application of this electrochemically modified electrode was employed for the determination of ambroxol in urine samples.

In this study, a selective, simple, and sensitive electrochemical method for the determination of theophylline was proposed based on a composite electrode. Electrochemical analysis of organic drug molecule, theophylline (TP) was investigated at eriochrome black-T and graphite powder composite electrode using different voltammetry techniques.. The linear response was obtained in the range of 1.0 x 10(-4) M to 10 x 10(-4) M with a detection limit LOD 20 nM. A possible electrochemical oxidation for theophylline involving two electrons and two protons was found and a suitable mechanism was proposed. For the analytical applications, pharmaceutical dose form and human urine sample analysis were performed. Various interferents were used to investigate the interference in the analytical application, and it was found that the proposed method could be well adopted for clinical trials and real sample analysis.

The electro-oxidation of valacyclovir has been studied at a glassy carbon electrode in phosphate buffer media by using cyclic voltammetric technique. Effects of anodic peak potential (E-pa), anodic peak current (i(pa)), pH and heterogeneous rate constant (k(o)) have been discussed, single irreversible voltammogram was observed. The effects of scan rate, pH, concentration and temperature were evaluated. The electrode processes were shown to be diffusion controlled and irreversible involving adsorption effects. The electro-oxidation product of valacyclovir has been identified by MALDI2-((2-amine-6,8-dioxo-7,8-dihydro-3H-purin9(6H)-yl) methoxy)ethyl2-amino-3-methylbutanoate), involving 2-electron and 2-porton oxidation. Thermodynamic parameters such as activation energy E-a=27.51 kJmol(-1), enthalpy Delta H-#=25.03 kJmol(-1), entropy Delta S-#=-284.8 JK(-1)mol(-1), Gibbs free energy Delta G(#)=109.9 kJmol(-1) and Arrhenius factor, logA=-2.08 and analytical parameters linearity range 5.0x10(-3) to 7.5x10(-5) M, LOD=1.44 mu M, LOQ= 4.83 mu M and RSD=5.26% were calculated and presented.