Sharanappa T. Nandibewoor

Kinetic, mechanistic and spectral studies for the oxidation of sulfanilic acid by alkaline hexacyanoferrate(III)

Abstract The kinetics of oxidation of sulfanilic acid ( p -aminobenzenesulfonic acid) by hexacyanoferrate(III) in alkaline medium was studied spectrophotometrically. The reaction showed first order kinetics in hexacyanoferrate(III) and alkali concentrations and an order of less than unity in sulfanilic acid concentration (SAA). The rate of reaction increases with increase in alkali concentration. Increasing ionic strength increases the rate but the dielectric constant of the medium has no significant effect on the rate of the reaction. A retarding effect was observed by one of the products i.e. hexacyanoferrate(II) (HCF(II)). A mechanism involving the formation of a complex between sulfanilic acid and hexacyanoferrate(III) has been proposed. The reaction constants involved in the mechanism are evaluated. There is a good agreement between the observed and calculated rate constants under different experimental conditions. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism.

Study on the interaction between antibacterial drug and bovine serum albumin: A spectroscopic approach

The binding of sulfamethoxazole (SMZ) to bovine serum albumin (BSA) was investigated by spectroscopic methods viz., fluorescence, FT-IR and UV-vis absorption techniques. The binding parameters have been evaluated by fluorescence quenching method. The thermodynamic parameters, Delta H degrees, DeltaS degrees and Delta G degrees were observed to be -58.0 kJ mol(-1), -111 J K(-1)mol(-1) and -24 kJ mol(-1), respectively. These indicated that the hydrogen bonding and weak van der Waals forces played a major role in the interaction. Based on the Forsters theory of non-radiation energy transfer, the binding average distance, r, between the donor (BSA) and acceptor (SMZ) was evaluated and found to be 4.12 nm. Spectral results showed the binding of SMZ to BSA induced conformational changes in BSA. The effect of common ions and some of the polymers used in drug delivery for control release was also tested on the binding of SMZ to BSA. The effect of common ions revealed that there is adverse effect on the binding of SMZ to BSA.

Electrochemical behavior of an antiviral drug acyclovir at fullerene-C60-modified glassy carbon electrode

Electrochemical oxidation of acyclovir at fullerene-C(60)-modified glassy carbon electrode has been investigated using cyclic and differential pulse voltammetry. In pH 7.4 phosphate buffer, acyclovir showed an irreversible oxidation peak at about 0.96V. The cyclic voltammetric results showed that fullerene-C(60)-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of acyclovir. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the acyclovir determination by differential pulse voltammetry. Effects of anodic peak potential (E(p)/V), anodic peak current (I(p)/μA) and heterogeneous rate constant (k(0)) have been discussed. Under optimized conditions, the concentration range and detection limit were 9.0×10(-8) to 6.0×10(-6)M and 1.48×10(-8)M, respectively. The proposed method was applied to acyclovir determination in pharmaceutical samples and human biological fluids such as urine and blood plasma as a real sample. This method can also be employed in quality control and routine determination of drugs in pharmaceutical formulations.

Voltammetric behavior of theophylline and its determination at multi-wall carbon nanotube paste electrode

The voltammetric behavior of theophylline was investigated using cyclic and differential-pulse voltammetric techniques. The cyclic voltammetric results indicate that multi-wall carbon nanotube paste electrode can remarkably enhance electrocatalytic activity toward the oxidation of theophylline in pH 3.0 phosphate buffer solution than the carbon paste electrode. The oxidation of theophylline was observed to be a two-electron process, irreversible with diffusion character. Effects of anodic peak potential (E(p)), anodic peak current (I(p)) and heterogeneous rate constant (k(o)) have been discussed. Under optimal conditions, the anodic peak current was proportional to theophylline concentration in the range of 2.0×10(-6) to 1.5×10(-4)M with a detection limit of 1.97×10(-8)M using differential pulse voltammetry. The proposed method was employed to determine theophylline in pharmaceutical formulations and urine as a real sample.

Electro-oxidation and determination of trazodone at multi-walled carbon nanotube-modified glassy carbon electrode

A simple and rapid electrochemical method was developed for the determination of trace-level trazodone, based on the excellent properties of multi-walled carbon nanotubes (MWCNTs). The MWCNT-modified glassy carbon electrode was constructed and the electrochemical behavior of trazodone was investigated in detail. The cyclic voltammetric results indicate that MWCNT-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of trazodone in neutral solutions. It leads to a considerable improvement of the anodic peak current for trazodone, and allows the development of a highly sensitive voltammetric sensor for the determination of trazodone. Trazodone could effectively accumulate at this electrode and produce two anodic peaks at about 0.73 V and 1.00 V. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the trazodone determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit are 0.2-10 microM and 24 nM, respectively for trazodone. The proposed method was successfully applied to trazodone determination in pharmaceutical samples. The analytical performance of this sensor has been evaluated for detection of analyte in urine as a real sample.

Osmium(VIII)/ruthenium(III) catalysis of periodate oxidation of acetaldehyde in aqueous alkaline medium

Os(VIII) and Ru(III) catalysis of the periodate oxidation of acetaldehyde in aqueous alkaline medium was investigated. The catalytic efficiency is Ru(III)<Os(VIII). The product of oxidation in both cases is acetate and IO3−. The stoichiometry is the same in both catalyzed reactions, i.e. [IO4−]:[CH3CHO] = 1:1. Probable mechanisms are proposed and discussed. The reaction constants involved in the mechanisms are derived.

Voltammetric oxidation and determination of cinnarizine at glassy carbon electrode modified with multi-walled carbon nanotubes

The voltammetric oxidation of cinnarizine was investigated. In pH 2.5 Britton-Robinson buffer, cinnarizine shows an irreversible oxidation peak at about 1.20 V at a multi-walled carbon nanotube (MWCNT)-modified glassy carbon electrode. The cyclic voltammetric results indicate that MWCNT-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of cinnarizine. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the cinnarizine determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit are 9.0x10(-8) to 6.0x10(-6) M and 2.58x10(-9) M, respectively for cinnarizine. The proposed method was successfully applied to cinnarizine determination in pharmaceutical samples. The analytical performance of this sensor has been evaluated for the detection of analyte in urine as a real sample.

Kinetics of osmium(VIII) catalysis of periodate oxidation of DMF in aqueous alkaline medium

SummaryThe osmium(VIII) catalysed IO4− oxidation of DMF in aqueous alkaline medium follows the rate law: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbiqaaaRfcqGHsi% slcaqGKbWaamWaaeaacaqGjbGaae4tamaaDaaaleaacaaI0aaabaGa% eyOeI0caaaGccaGLBbGaayzxaaGaai4laiaabsgaieGacaWF0bGaa8% xpamaalaaabaGaa83Aaiaa-TeadaWgaaWcbaacbaGaa4NmaaqabaGc% caWGlbWaaSbaaSqaaiaaiodaaeqaaOGaai4waiaabseacaqGnbGaae% Oraiaac2facaGGBbGaae4taiaabIeadaahaaWcbeqaaiabgkHiTaaa% kiaac2facaGGBbGaae4taiaabohadaahaaWcbeqaaiaabAfacaqGjb% GaaeysaiaabMeaaaGccaGGDbWaaSbaaSqaaiaa+rfaaeqaaaGcbaGa% aGymaiabgUcaRiaa-TeadaWgaaWcbaGaa4NmaaqabaGccaWGlbWaaS% baaSqaaiaaiodaaeqaaOGaai4waiaabseacaqGnbGaaeOraiaac2fa% caGGBbGaae4taiaabIeadaahaaWcbeqaaiabgkHiTaaakiaac2facq% GHRaWkcaWFlbWaaSbaaSqaaiaa+jdaaeqaaOGaai4waiaab+eacaqG% ibWaaWbaaSqabeaacqGHsislaaGccaGGDbaaaaaa!6B43!

Permanganate oxidation of chromium(III) in aqueous alkaline medium: a kinetic study by the stopped-flow technique

- {\text{d}}\left[ {{\text{IO}}_4^ - } \right]/{\text{d}}t = \frac{{kK_2 K_3 [{\text{DMF}}][{\text{OH}}^ - ][{\text{Os}}^{{\text{VIII}}} ]_T }}{{1 + K_2 K_3 [{\text{DMF}}][{\text{OH}}^ - ] + K_2 [{\text{OH}}^ - ]}}