A.M Beltagi

Determination of Norfloxacin by square-wave adsorptive voltammetry on a glassy carbon electrode

The adsorptive and electrochemical behavior of norfloxacin on a glassy carbon electrode were investigated by cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated that the process was irreversible and fundamentally controlled by adsorption. To obtain a good sensitivity, the solution conditions and instrumental parameters were studied using square-wave voltammetry. In acetate buffer of pH 5.0, norfloxacin gave a sensitive adsorptive oxidative peak at 0.920 V (versus Ag-AgCl). Applicability to measurement of norfloxacin at submicromolar levels in urine samples was illustrated. The peak current was linear with the norfloxacin concentration in the range 5-50 microg ml(-1) urine. The detection limit was 1.1 microg ml(-1) urine.

Determination of the antibiotic drug pefloxacin in bulk form, tablets and human serum using square wave cathodic adsorptive stripping voltammetry

A simple, rapid, reliable and fully validated square wave cathodic adsorptive stripping voltammetric procedure has been developed for the determination of the antibiotic pefloxacin drug in bulk form, tablets and human serum, based on its electrochemical reduction at a hanging mercury drop electrode. The Britton-Robinson buffer of pH 7.0 was found to be reasonable as a supporting electrolyte for assay of the drug. Pefloxacin drug, at the optimized conditions, showed a single 2-electron well-defined peak at -1.07 V (versus Ag/AgCl/KCl(s)) using an accumulation potential of -0.40 V. This peak may be attributed to the reduction of the C=O group. A mean recovery of 99.54%+/-0.23 and a detection limit of 1.65 x 10(-10) M pefloxacin were achieved. After being validated, the proposed procedure was successfully applied for the determination of the drug in tablets and human serum with mean recoveries of 99.57+/-0.48 and 98.55+/-0.78%, respectively. A detection limit of 4.50 x 10(-10) M was achieved for the determination of the drug in human serum. Results of the proposed procedure were comparable with those obtained by reported methods.

Simultaneous determination of cadmium (II), lead (II), copper (II) and mercury (II) by square-wave anodic stripping voltammetry at a montmorillonite-calcium modified carbon paste electrode

A simple and efficient montmorillonite-calcium modified carbon paste electrode (MMT-Ca modified CPE) was constructed for simultaneous trace determination of Cd(II), Pb(II), Cu(II) and Hg(II). The MMT-Ca modified CPE significantly enhances the voltammetric stripping peak current magnitudes of the investigated metal ions compared to the bare CPE due to the large cation-exchange capacity and the strong adsorptive property of montmorillonite-Ca clay. A fully validated simple, sensitive, selective and precise square-wave anodic stripping voltammetric method was developed for the simultaneous trace determination of Cd(II), Pb(II), Cu(II) and Hg(II) in various water samples using a fabricated 10% (w/w) MMT-Ca modified CPE. The achieved limits of detection of Cd(II) 0.54 µg L−1, Pb(II) 0.30 µg L−1, Cu(II) 0.75 µg L−1 and Hg(II) 1.05 µg L−1 indicating the high sensitivity of the described SW-AS voltammetry method for the assay of these metal ions in aqueous solutions. The method was successfully applied for analysis of tap water, bottled natural water and seawater samples.

Electrochemical reduction of meloxicam at mercury electrode and its determination in tablets.

The electrochemical reduction of meloxicam has been studied at a mercury electrode using various electrochemical methods in aqueous solutions over a wide pH range. The reduction of the drug produced a single reduction step in acidic media, whereas in slightly acidic and neutral media two reduction steps were observed. In alkaline media meloxicam shows a single pH-independent reduction step. The irreversibility of the electrode process was verified by different criteria. At all pH values, reactant adsorption at mercury electrode was observed. The mechanism of reduction was discussed. Using differential-pulse voltammetry, the drug yielded a well-defined voltammetric response in Britton-Robinson buffer solution, pH 4.0 at -1.286 V (vs. Ag/AgCl). This process could be used to determine meloxicam concentration in the range 1.0 x 10(-8)-5.0 x 10(-6) M. The method was successfully applied for the analysis of meloxicam in the tablet dosage form.

Determination of trimetazidine HCl by adsorptive stripping square-wave voltammetry at a glassy carbon electrode

The adsorptive and electrochemical behavior of trimetazidine hydrochloride on a glassy carbon electrode were investigated in acetate buffer solution by using cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated the oxidation of trimetazidine hydrochloride at the electrode surface through a single two-electron irreversible step and fundamentally controlled by adsorption. The solution condition and instrumental parameters were optimized for the determination of the authentic drug using adsorptive square wave stripping voltammetry. Trimetazidine hydrochloride gave a sensitive adsorptive oxidative peak at 0.750 V (vs. Ag/AgCl). The oxidation peak was used to determine authentic trimetazidine hydrochloride concentration in the range 5.0 x 10(-8)-5.0 x 10(-6) M with a detection limit of 2.0 x 10(-8) M. The procedure was successfully applied for assay of trimetazidine hydrochloride in the tablet dosage form (Vastarel). A mean recovery of 94.7% with a relative standard deviation (R.S.D.) of 0.88% was obtained. Applicability to assay the drug in urine samples was illustrated. The peak current was linear with the drug concentration in the range 17-85 microg per ml urine. The detection limit was 1.7 microg ml(-1) urine.