Simultaneous voltammetric sensing of Zn2+, Cd2+, and Pb2+ using an electrodeposited Bi-Sb nanocomposite modified carbon paste electrode.

A sensor for detecting Zn2+, Cd2+, and Pb2+ ions simultaneously based on the square wave anodic stripping response at a bismuth antimony (Bi-Sb) nanocomposite electrode was developed. The electrode was prepared in situ by electrodepositing bismuth and antimony on the surface of a carbon-paste electrode (CPE) while also reducing the analyte metal ions. The structure and performance of the Bi-Sb/CPE electrode were studied using scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and cyclic voltammetry. Operational conditions including the concentration of Sb and Bi, the type of electrolyte, pH, and preconcentration conditions were optimized. The linear ranges were determined to be 5-200 µg L-1 for Zn2+, 1-200 µg L-1 for Cd2+, and 1-150 µg L-1 for Pb2+ with the optimized parameters. The limits of detection were 1.46 µg L-1, 0.27 µg L-1, and 0.29 µg L-1 for Zn2+, Cd2+, and Pb2+, respectively. Furthermore, the Bi-Sb/CPE sensor is capable of selective determination of the target metals in the presence of the common cationic and anionic interfering species (Na+, K+, Ca2+, Mg2+, Fe3+, Mn2+, Co2+, Cl-, SO4 2- and HCO3 -). Finally, the sensor was successfully applied to the simultaneous determination of Zn2+, Cd2+, and Pb2+ in a variety of real-world water 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).

Voltammetric studies on the antibiotic drug cefoperazone quantification and pharmacokinetic studies.

A fully validated simple, sensitive and selective square-wave stripping voltammetry procedure was described for the trace quantification of cefoperazone in bulk form, formulations and human serum/plasma. The procedure was based on reduction of the adsorbed drug onto a hanging mercury drop electrode. The procedural conditions were optimized as: frequency=60Hz, scan increment=8mV, pulse amplitude=25mV, preconcentration potential=-0.3V (versus Ag/Ag/KCl(s)), preconcentration duration=60-150s and an acetate buffer of pH 4.2 as a supporting electrolyte. A limit of detection of 4.5x10(-10)M and a limit of quantitation of 1.5x10(-9)M bulk cefoperazone were achieved following preconcentration of the drug onto the hanging mercury drop electrode for 150s. The proposed square-wave adsorptive cathodic stripping voltammetric procedure was successfully applied for trace quantification of cefoperazone in human serum and plasma. The achieved limits of detection and quantitation of the drug in human serum were 6x10(-10)M (0.375ngml(-1)) and 2x10(-9)M (1.250ngml(-1)), respectively. The pharmacokinetic parameters of cefoperazone in plasma of hospitalized volunteers were successfully estimated.

A validated stripping voltammetric procedure for quantification of the anti-hypertensive and benign prostatic hyperplasia drug terazosin in tablets and human serum.

The electrochemical behavior of terazosin at the hanging mercury drop electrode was studied in Britton-Robinson buffer (pH 2-11), acetate buffer (4.5-5.5), and in 0.1M solution of each of sodium sulfate, sodium nitrate, sodium perchlorate and potassium chloride as supporting electrolytes. The square-wave adsorptive cathodic stripping voltammogram of terazosin exhibited a single well-defined two-electron irreversible cathodic peak which may be attributed to the reduction of CO double bond of the drug molecule. A fully validated, simple, high sensitive, precise and inexpensive square-wave adsorptive cathodic stripping voltammetric procedure was described for determination of terazosin in bulk form, tablets and human serum. A mean recovery for 1x10(-8)M terazosin in bulk form, following preconcentration onto the hanging mercury drop electrode for 60s at a -1.0V (versus Ag/AgCl/KCl(s)), of 99+/-0.7% (n=5) was obtained. Limits of detection (LOD) and quantitation (LOQ) of 1.5x10(-11) and 5x10(-11)M bulk terazosin were achieved, respectively. The proposed procedure was successfully applied to determination of the drug in its Itrin((R)) tablets and human serum samples. The achieved LOD and LOQ of the drug in human serum samples were 5.3x10(-11) and 1.8x10(-10)M THD, respectively. The pharmacokinetic parameters of the drug in human plasma were estimated as: C(max)=77.5ngml(-1), t(max)=1.75h, AUC(0-t)=602.3nghml(-1), K(e)=0.088h(-1) and t(1/2)=11.32h) which are favorably compared with those reported in literature.

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.

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).

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.

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 ketorolac in human serum by square wave adsorptive stripping voltammetry.

The adsorption behavior of ketorolac on a hanging mercury drop electrode (HMDE) was explored by square-wave and cyclic voltammetry. The square wave voltammetric response of ketorolac depends on the parameters of the square wave voltammetry excitation signal as well as on the pH of the medium and the accumulation time. The drug was accumulated at HMDE and a well-defined peak was obtained at -1.41 V versus. Ag/AgCl (saturated KCl) in acetate buffer of pH 5.0. A square-wave adsorptive stripping voltammetric method for the quantitative determination of ketorolac was developed. The linear concentration range was 1x10(-10)-1x10(-8) when using 300 s accumulation at -0.8 V. The detection limit of ketorolac was 1.0x10 (-11)M . The precision was excellent with relative standard deviation of 3.85% at concentration of 5x10 (-8)M after 60 s accumulation time. Applicability to serum samples was illustrated. A detection limit of 14 ng per ml of serum was obtained.

Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode.

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.