Jayant I. Gowda

MWCNT–CTAB modified glassy carbon electrode as a sensor for the determination of paracetamol

An electrochemical sensor for the sensitive detection of paracetamol (PCM) was developed by constructing a glassy carbon electrode (GCE) modified with multiwalled carbon nanotube–cetyltrimethyl ammonium bromide (MWCNT–CTAB). Modification improves the redox kinetics of PCM with increased current intensity. A similar modification at CTAB modified GCE did not result in an impressive charge transfer. The detection limit of PCM was determined from a differential pulse voltammetric (DPV) study and found to be 4.82 × 10−9 M with a linear dynamic range of 4.0 × 10−7 M to 4.0 × 10−6 M. The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of a large excess of interferents and the response is fast, stable, reliable, resistant to biofouling and can be applied for real sample analysis in medical, pharmaceutical and biotechnological sectors. Kinetic parameters were determined using electrochemical approaches. The practical analytical application of this electrode was demonstrated by measurement of the PCM content in a PYREMOL 650 tablet and real sample analysis.

Binding and conformational changes of human serum albumin upon interaction with 4-aminoantipyrine studied by spectroscopic methods and cyclic voltammetry

The interactions of 4-aminoantipyrine (AAP) with human serum albumin (HSA) have been studied by UV-visible spectroscopy, fluorescence spectroscopy and cyclic voltammetry. The binding of 4-aminoantipyrine quenches the HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 10(5) M(-1). The experimental results showed that AAP effectively quenched the intrinsic fluorescence of HSA via dynamic type of quenching. In addition, according to the synchronous fluorescence spectra of HSA in presence of 4-aminoantipyrine, the tryptophan residue of the proteins are most perturbed by the binding process. The number of binding sites, the binding constant, site probe study, some common metal ions effect and the thermodynamic parameters were calculated.

Fabrication of multiwalled carbon nanotube-surfactant modified sensor for the direct determination of toxic drug 4-aminoantipyrine

A multi-walled carbon nanotube (MWCNT)-cetyltrimethylammonium bromide (CTAB) surfactant composite modified glassy carbon electrode (GCE) was developed as a novel system for the determination of 4-aminoantipyrine(AAP). The oxidation process was irreversible over the pH range studied and exhibited a diffusion controlled behavior. All experimental parameters were optimized. The combination of MWCNT-CTAB endows the biosensor with large surface area, good biological compatibility, electricity and stability, high selectivity and sensitivity. MWCNT-CTAB/GCE electrode gave a linear response for AAP from 5.0×10−9 to 4.0×10−8 M with a detection limit of 1.63×10−10 M. The modified electrode showed good selectivity against interfering species and also exhibited good reproducibility. The present electrochemical sensor based on the MWCNT-CTAB/GCE electrode was applied to the determination of AAP in real samples.

Simultaneous electrochemical determination of 4-aminophenazone and caffeine at electrochemically pre-treated graphite pencil electrode

A new and sensitive electroanalytical method for simultaneous determination of selected drugs, 4-aminophenazone (4-AP) and caffeine (CAF) has been developed and validated. Cyclic voltammetry (CV) was used to study the electrochemical behavior of the drugs, while differential pulse voltammetry (DPV) was used to determine 4-AP and CAF simultaneously. A pre-treated graphite pencil electrode (PTGPE) was used as the working electrode, a Ag/AgCl (3.0 M KCl) electrode served as the reference electrode, and a platinum wire as the auxiliary electrode. Determination of drugs was performed in phosphate buffer solution (PBS) of pH = 3.0. The separation of the oxidation peak potentials for 4-AP–CAF was found to be 0.930 V. This difference was large enough to determine 4-AP and CAF individually and simultaneously. The dependence of the current on pH, concentration and scan rate was investigated to optimize the experimental conditions for simultaneous determination. The calibration plots for both the drugs were linear in certain concentration ranges. The linearity range for 4-AP was 1 μM to 11 μM and for CAF 1 μM to 9 μM, the concentration of each drug was varied by keeping the other constant, and achieved lower detection limit of 7.96 × 10−8 M for 4-AP and 9.81 × 10−9 M for CAF. The developed method was found to be precise, selective and rapid for the simultaneous determination of 4-AP and CAF. The proposed method has been applied for the determination of 4-AP and CAF in real samples.

Oxidation of xylitol by a silver(III) periodate complex in the presence of osmium(VIII) as a homogeneous catalyst

The kinetics of the osmium (Os(VIII)) catalyzed oxidation of xylitol (XYL) by a silver(III) periodate complex (diperiodatoargentate(III)) (DPA) in an aqueous alkaline medium at 298 K and at a constant ionic strength of 0.06 mol dm−3 was studied spectrophotometrically. The reaction between DPA and xylitol in an alkaline medium exhibits 1:2 stoichiometry (XYL:DPA). The reaction is of first order in [Os(VIII)] and [DPA] and has a negative fractional order in [IO4−]. It is apparent that it has less than the unit order in [XYL] and [OH−] under the experimental conditions. The main oxidation product was identified as 2,3,4,5-tetrahydroxypentanoic acid by FT-IR and LC-MS spectral studies. A probable mechanism was proposed and discussed. The activation parameters with respect to the slow step of the mechanism were computed and discussed and thermodynamic quantities were also calculated. The active species of the catalyst and oxidant have been identified.

Pretreated Graphite Pencil Electrode Based Voltammetric Sensing of Albendazole

Abstract Electrochemical behavior of albendazole was investigated at a pre-treated pencil graphite electrode (PTPGE) by cyclic voltammetry in phosphate buffer solution. The Pre-treated pencil graphite electrode showed excellent electro-catalytic activity towards the oxidation of albandazole in phosphate buffer solution of pH 3.0. From the electrochemical studies of scan rate, the overall electrode process was diffusion controlled. The pH effect suggested that equal number of protons and electrons were involved in the electrochemical detection of albendazole. Under the optimum conditions the peak current was linear to the concentration of albandazole in the range 250 μM to 1450 μM for PTPGE and the detection limit (LOD) was found to be 5.42 nM. The interference studies showed that the modified electrode exhibited excellent selectivity in the presence of large excess of interfering substances. The proposed method was successfully applied for the determination of albendazole in the spiked urine and pharmaceutical samples.

Electrochemical Determination of Albendazole at Glassy Carbon Electrode.

In this article, the electrochemical behavior on a glassy carbon electrode (GCE) was investigated and the electrochemical parameters of albendazole (ALB) were calculated. ALB effectively accumulated on the GCE surface and caused a pair of redox peaks at around 1.095 V and 1.028 V and an oxidation peak at 0.844 V (versus saturated calomel electrode) in 0.2 M phosphate buffer solution (pH 3.0). Under optimized conditions, the anodic peak current was linear to the ALB concentration the range of 1.5 × 10-7 M to 4.0 × 10-5 M. The regression equation was: Ipa (10-6 A) = 0.79 [ALB] (μM) + 0.84 (R2 = 0.982). The detection limit 6.08 × 10-8 M was obtained. The proposed method was successfully used to determine ALB content in tablet samples, with satisfactory results.

Spectroscopic and mechanistic investigations into oxidation of aspartame by diperiodatocuprate(III) in aqueous alkaline medium

Abstract The oxidation of aspartame (ASP) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at 298 K and a constant ionic strength of 0.30 mol dm−3 was studied spectrophotometrically. The reaction between aspartame and diperiodatocuprate(III) in alkaline medium exhibits 1:6 stoichiometry in the reaction. The order of the reaction with respect to [diperiodatocuprate(III)] was unity, while the apparent order with respect to [aspartame] was less than unity over the concentration range studied. The rate of the reaction increased with increase in [OH−] whereas the rate decreased with increase in []. Increasing the ionic strength of the medium increased the rate. The main products were identified by FT-IR, NMR, and LC-MS spectral studies. The probable mechanism was proposed. The activation parameters with respect to slow step of the mechanism were computed and discussed. Thermodynamic quantities were also calculated. Kinetic studies suggest that [Cu(H2IO6)(H2O)2] is the reactive species of Cu(III).

Mechanism of Oxidation of Xylitol by a New Oxidant, Diperiodatoargentate (III), in Aqueous Alkaline Medium

The oxidation of xylitol (XYL) by Ag (III) periodate complex (DPA) in aqueous alkaline medium at 298 K and a constant ionic strength of 0.06 mol dm−3 was studied spectrophotometrically. The reaction between xylitol and DPA in alkaline medium exhibits 1:2 stoichiometry in the reaction. The order of the reaction with respect to [DPA] was unity while the apparent order with respect to [XYL] was less than unity over the concentration range studied. The rate of the reaction increased with increase in [OH−] whereas the rate decreased with increase in [IO−4]. The main products were identified by FT-IR and LC-MS spectral studies. The probable mechanism was proposed. The activation parameters with respect to slow step of the mechanism were computed and are discussed. Thermodynamic quantities were also calculated. Kinetic studies suggest that [Ag (H2IO6) (H2O) 2] is the reactive species of Ag (III).