Mohamed M. Ghoneim

Oxidation of Levafix CA reactive azo-dyes in industrial wastewater of textile dyeing by electro-generated Fenton's reagent

The indirect electrochemical removal of pollutants from effluents has become an attractive method in recent years. Removal (decolorization and mineralization) of Levafix Blue CA and Levafix Red CA reactive azo-dyes from aqueous media by electro-generated Fentons reagent (Fe(2+)/H(2)O(2)) using a reticulated vitreous carbon cathode and a platinum gauze anode was optimized. Progress of oxidation (decolorization and mineralization) of the investigated azo-dyes with time of electro-Fentons reaction was monitored by UV-visible absorbance measurements, Chemical oxygen demand (COD) removal and HPLC analysis. The results indicated that the electro-Fentons oxidation system is efficient for treatment of such types of reactive dyes. Oxidation of each of the investigated azo-dyes by electro-generated Fentons reagent up to complete decolorization and approximately 90-95% mineralization was achieved. Moreover, the optimized electro-Fentons oxidation was successfully applied for complete decolorization and approximately 85-90% mineralization of both azo-dyes in real industrial wastewater samples collected from textile dyeing house at El-Mahalla El-Kobra, Egypt.

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.

Electrochemical behavior of the antituberculosis drug isoniazid and its square-wave adsorptive stripping voltammetric estimation in bulk form, tablets and biological fluids at a mercury electrode

Isoniazid, pyridine-4-carboxylic acid hydrazide, is an antituberculosis-agent, which is used to prevent the development of clinical tuberculosis. A validated square-wave adsorptive cathodic stripping voltammetric procedure for the trace determination of the bulk drug at the hanging mercury drop electrode (HMDE) has been developed. Under the optimized conditions, (accumulation potential=-0.9 V, accumulation time=50-300 s, scan increment=8 mV, pulse-amplitude=25 mV, frequency=120 Hz and acetate buffer at pH 5.5) isoniazed generated two irreversible cathodic peaks. The first peak current showed a linear dependence with the drug concentration over the range 5 x 10(-10)-21 x 0(-6) M. The mean percentage recoveries, based on the average of five replicate measurements, for 7 x 10(-9) and 5 x 10(-8) M isoniazid were 97.71+/-2.93 and 99.76+/-0.77, respectively. The achieved limits of detection (LOD) and quantitation (LOQ) were 1.18 x 10(-10) and 3.93 x 10(-10) M isoniazid, respectively. The procedure was applied to the assay of the drug in tablets (Isocid and T.B. Zide), spiked human serum and urine with mean percentage recoveries of 97.81+/-1.49, 97.45+/-2.09, and 97.08+/-1.06, respectively. The limits of detection of 1.47 x 10(-9) and 2.4 x 10(-8) M, and quantitation of 4.9 x 10(-9) and 8 x 10(-8) M drug in human serum and urine, respectively, were achieved. The mean values of the various pharmackinetic parameters of isoniazid (C(max), T(max), t(1/2), AUC, and K(e)), estimated from analysis of plasma of two volunteers by means of the proposed procedure were similar to literature values.

Polarographic behaviour of loratadine and its direct determination in pharmaceutical formulation and human plasma by cathodic adsorptive stripping voltammetry.

The polarographic behaviour of the antihistaminic drug loratadine has been investigated in B.R. buffer solution of different pH values. Contradictory to that mentioned before in a previously published work, loratadine is electro-active at the mercury electrode. In B.R. buffer solution of pH values > or =6 it is reduced via a single 2-electrons irreversible wave corresponding to saturation of carbon-nitrogen double bond of the pyridine ring. The electrode reaction pathway was proposed and discussed. A sensitive differential pulse stripping voltammetric method based on controlled adsorptive accumulation of loratadine on a hanging mercury drop electrode has been developed for its direct determination at nanomolar concentrations without nitration of the drug. The optimized conditions for the direct cathodic adsorptive stripping voltammetric determination of the drug are: 0.1 M sodium hydroxide solution as a supporting electrolyte, accumulation potential, -1.2 V; accumulation time, 30 s; scan rate, 2-5 mV x s(-1) and pulse amplitude 100 mV. The proposed procedure was applied for the assay of loratadine in pharmaceutical formulation and human plasma. The average recoveries were 99.32-99.44 and 100.33-102.99% with the RSD 0.27-0.42 and 0.39-0.90% in pharmaceutical formulation and human plasma, respectively. The limits of detection of 1.60x10(-7) and 1.25x10(-7) M loratadine were found in pharmaceutical formulation and human plasma, respectively.

Adsorptive stripping voltammetric determination of the anti-inflammatory drug celecoxib in pharmaceutical formulation and human serum

Celecoxib is a cyclooxygenase inhibitor, that has been recently and intensively prescribed as an anti-inflammatory drug in rheumatic osteoarthritis. A robust, highly reliable and reproducible square-wave (SW) adsorptive cathodic stripping voltammetric procedure was developed for the determination of celecoxib in pharmaceutical formulation and human serum. The analytical procedure was based on the reduction of the CN of the pyrazole ring of the drug molecule at the mercury electrode surface in Britton-Robinson buffer of pH 7.0. The SW adsorptive cathodic stripping voltammogram of celecoxib showed a single well-defined peak at -1.54 V (vs. Ag/AgCl/KCl(s)) using an accumulation potential of -0.70 V, frequency of 120 Hz, scan increment of 10 mV and pulse amplitude of 25 mV. Repeatability was examined for 1 x 10(-8) M CXB drug solution after 30 s pre-concentration and a mean recovery of 99.4+/-0.4% (n=5) was achieved. For 90 s preconcentration, a linear concentration range of 1 x 10(-9)-2 x 10(-8) M CXB and a detection limit of 1.86 x 10(-10) M were achieved. The proposed procedure was successfully applied for the determination of the drug in capsules and human serum with mean recoveries of 101.5+/-0.6 and 98.8+/-1.1%, respectively. A detection and quantitation limits of 1.0 x 10(-9) M (0.4 ng ml(-1)) and 4.7 x 10(-9) M (1.3 ng ml(-1)) were achieved for the determination of the drug in human serum. Moreover, the procedure was useful for study of the pharmacokinetic profile of celecoxib in a healthy volunteer after administration of a single oral dose (celebrex, 200 mg).

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.

Development of a voltammetric procedure for assay of the antihistamine drug hydroxyzine at a glassy carbon electrode: Quantification and pharmacokinetic studies.

An electrochemical study of hydroxyzine at a glassy carbon electrode was carried out in the Britton-Robinson universal buffer of pH 2-11. Hydroxyzine was oxidized in a single two-electron irreversible process controlled mainly by adsorption. A simple, sensitive and time-saving square-wave adsorptive anodic stripping voltammetric procedure has been developed for determination of hydroxyzine in its commercial tablets and human serum without prior extraction. The optimized procedural conditions were: frequency=120Hz, scan increment=10mV, pulse-amplitude=25mV, accumulation potential=-0.3V, accumulation time=90-300s and a Britton-Robinson universal buffer of pH 4 as a supporting electrolyte. Mean recoveries of 100.5+/-0.71 and 98.6+/-1.12% (n=5) were achieved for assay of hydroxyzine in Atarax 10 and 25mg dosage forms, respectively. Limit of detection of 1.5x10(-8)molL(-1) (5.624ngmL(-1)) and limit of quantitation of 5.0x10(-8)molL(-1) (18.746ngmL(-1)) were achieved in human serum with a mean recovery of 98.4+/-1.22%, without prior extraction of the drug. Moreover, the described procedure was applied for evaluating the pharmacokinetic parameters of hydroxyzine in plasma of two healthy volunteers after administration of a single oral dose (Atarax)-25mg).

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.

Voltammetric behavior and assay of the contraceptive drug levonorgestrel in bulk, tablets, and human serum at a mercury electrode

The cyclic voltammograms of levonorgestrel (LNG) in Britton-Robinson buffers of pH 2-11 at the hanging mercury drop electrode showed a single two-electron irreversible cathodic peak over the whole pH range. This peak may be attributed to the reduction of the 3-keto-delta-4-group in the A-ring of the LNG molecule. The interfacial adsorptive character of levonorgestrel onto the surface of the hanging mercury drop electrode was identified by means of both cyclic voltammetry and chronocoulometry techniques. A simple, sensitive, and selective square-wave adsorptive cathodic stripping voltammetric procedure was developed for the quantitation of levonorgestrel. Under the optimized operational conditions, the maximum developed stripping voltammetric peak current showed a linear response with concentration of the bulk LNG substance. The achieved limits of detection (LOD) and quantitation (LOQ) were 6.7x10(-10) and 2.2x10(-9)M, or 4.8x10(-10) and 1.6x10(-9)M, following accumulation onto the hanging mercury drop electrode for 90s or 150s, respectively. The developed procedure was successfully applied to the determination of levonorgestrel in tablets, in spiked human serum, and in real plasma samples of healthy female volunteers following an oral administration of a 30-mug LNG single dose. The pharmacokinetic parameters (C(max)=1.05ngml(-1), t(max)=2.4h and AUC(0-t)=16.5nghml(-1)) were estimated and favorably compared to those reported in literature for equivalent dose.