Mahmoud A. Ghandour

Cathodic adsorptive stripping voltammetric determination of uranium with potassium hydrogen phthalate.

The adsorption properties of dioxouranium (II)-Phathalate complexes onto hanging mercury drop electrode are exploited in developing a highly sensitive and selective stripping voltammetric procedure for the determination of uranium (VI). The reduction current of adsorbed complex ions of U(VI) was measured by both linear sweep (LSCSV) and differential pulse cathodic stripping voltammetry (DPCSV), preceded by a period of preconcentration onto the electrode surface. As low as 2x10(-9) mol dm(-3) (0.5 mug/l) and 2x10(-8) mol dm(-3) (4.8 mug/l) with accumulation time 240 and 120 s using DPCSV and LSCSV, respectively, have been determined successfully. The relative standard deviation of 2.2% at the 5 ppm level was obtained. The interferences of some metal ions and anions were studied. The application of this method was tested in the determination of uranium in superphosphate fertilizer.

Adsorptive Cathodic Stripping Voltammetric Determination of Hexavalent Chromium

Abstract A sensitive and selective voltammetric method of analysis is developed for determination of trace amounts of Cr(VI) ions in neutral nitrate phosphate media. This method is based on controlled adsorptive preconcentration of chromium species at Hanging Mercury Drop Electrode (HMDE). The adsorptive stripping response was evaluated with respect to preconcentration time and potential and dependence on composition of supporting electrolyte. As low as 5x10−9 mol L−1 (0.25 μg/L) and 1x109 mol L−1 (0.52 μg/L) Cr(VI) can be detected using Cathodic Linear Sweep Stripping Voltammetry (CLSSV) and Differential Pulse Cathodic Stripping Voltammetry (DPCSV), respectively. The precision of the method is satisfactory with a relative deviation of 1.24% with ten experiments at the 0.52 μg 1−1 Cr(VI) level. The effect of various cations, anions and surface active substances (SAS) in synthetic aqueous samples has been investigated.

Potentiometric studies on the complexes of tetracycline (TC) and oxytetracyclin (OTC) with some metal ions

SummaryThe interaction of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Al(III), and UO2(II) ions with tetracycline (TC) were studied by potentiometricpH titrations. The formation constants of the different binary complexes formed in such systems have been determined at 25±0.1°C and μ=0.1 moll−1 (NaNO3). PotentiometricpH equilibrium measurements have been made under the same conditions for the interaction of oxytetracycline (OTC) and Cu(II), Cd(II), Pb(II), and UO2(II). The formation of (1:1) binary complexes are inferred from the potentiometricpH tritration curves. The protonation constants ofTC andOTC were also determined under the same conditions and refined (ESAB2M computer program). The transition metal stability constants are consistent with the Irving-Williams series.ZusammenfassungDie Wechselwirkungen von Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Al(III) und UO2(II) Ionen mit Tetracyclin (TC) wurden mittels potentiometrischerpH-Titrationen untersucht. Die Komplexbildungskonstanten wurden bei 25±0.1°C und μ=0.1 mol/1(NaNO3) bestimmt. Unter den gleichen Bedingungen wurden die Komplexierung von Cu(II), Cd(II), Pb(II) und UO2(II) mit Oxytetracyclin (OTC) mittel potentiometrischerpH Gleichgewichtsmessungen untersucht. Aus den potentiometrischenpH-Titrationskurven ergab sich die Bildung von (1:1) binären Komplexen. Die Protonierungskonstanten vonTC undOTC wurden ebenfalls bestimmt und rechnerisch verfeinert (ESAB2M Computer Programm). Die Stabilitätskonstanten für die Übergangsmetalle stimmen mit der Irving-Williams Reihe überein.

Cathodic stripping voltammetry of the anticancer agent 5-fluorouracil and determination in urine

Cathodic stripping voltammetry was used to determine 5-fluorouracil (5-FU) in the presence of traces of Cu(II). It was found that the addition of 5 x 10(-9) mol dm(-3) Cu(II) to the measurement cell greatly enhanced the peak current of the adsorbed molecule. Different parameters were tested to optimize the conditions for the determination of 5-FU. The adsorbed form is reduced irreversibly. It was observed that by controlling the deposition potential, the technique could be directed to the determination of Cu(II) or the drug. The linear range was from 5 x 10(-9) to 6 x 10(-8) mol dm(-3) for 5-FU and from 6 x 10(-9) to 5 x 10(-8) mol dm(-3) for Cu(II). Detection limits of 4.6 x 10(-10) and 5 x 10(-10) mol dm(-3) were obtained for 5-FU and Cu(II), respectively. The method was applied to urine and molecules or ions which may interfere were studied.

Cephalosporin antibiotics at carbon paste and modified carbon paste electrodes in both aqueous and biological media

Abstract A sensitive voltammetric method has been developed for the oxidation and determination of the cephalosporin antibiotics Cefatrexyl, Velosef, Claforan, Cefobid and Rocephin at both carbon paste and modified fatty acid carbon paste electrodes. The electroanalytical technique used was direct current stripping voltammetry. The adsorptive stripping response was evaluated as a function of preconcentration time, preconcentration potential, modifier percentage and other variables. The effect of the interfering materials such as ascorbic acid, uric acid and some metal ions, i.e. Cu(II) and Fe(III), has also been taken into consideration. A detection limit down to 10 −8 M has easily been achieved. Application of the method to biological samples (e.g. urine and serum) has been assessed.

Adsorptive Cathodic Stripping Voltammetric Determination of Molybdenum in Synthetic Solutions and Environmental Samples

A sensitive and selective voltammetric methods has been developed for the determination of trace amounts of Mo(VI) ions. This method is based on controlled adsorptive preconcentration of molybdenum species on the hanging mercury drop electrode (HMDE) using mixtures of nitrate and phosphate as supporting electrolytes. The adsorptive stripping response was evaluated with respect to preconcentration time, potential and composition of supporting electrolyte. The method used is cathodic linear sweep stripping voltammetry (CLSSV). The detection limit found was 1610 78 M using 120 s. as accumulation time. The precision of the method is satisfactory with relative standard deviation of 1.4% with five replicates at 1610 76 M Mo(VI). The effect of various surface active substances (SAS) as well as different metal cations and anions in synthetic aqueous solutions has been investigated. Also this method has been applied for the determination of Mo(VI) in environmental samples; e.g., soil, natural water and indoor airborne particulate.

Cathodic adsorptive stripping voltammetric determination of muscle relaxant: gallamine triethiodide (flaxedil)

A sensitive and simple voltammetric method of analysis is developed for the determination of trace amounts of gallamine triethiode in phosphate media. This method is based on controlled adsorptive preconcentration of the relaxant onto a Hanging Mercury Drop Electrode (HMDE) whereby mercurous iodide salt(s) are formed. The technique used is Cathodic Linear Sweep Stripping Voltammetry (CLSSV). The adsorptive response was evaluated with respect to preconcentration time and potential. As little as 3 x 10(-9) mol dm(-3) i.e. 2.7 ppb flaxedil (proconcentration time 300 seconds) can be determined successfully. The application of this method was tested in the determination of flaxedil in pharmaceutical preparation (ampoules).

Copper (II), Lead (II) and Cadmium (II) Complexes with the Antiinflammatory Drugs Piroxicam and Tenoxicam

Abstract The chelating tendency of the antiinflammatory drugs piroxicam and tenoxicam towards copper (II), lead (II) and cadmium (II) ions has been investigated using both differential pulse polarography and cyclic voltammetry and the stability constants of the formed complexes have been compared. The effect of the nature of the supporting electrolyte, the pH and other parameters have also been considered. Tenoxicam exhibits relatively stronger chelating properties than piroxicam towards each ion despite of their structural similarity.

Electroreduction and determination of Pipril (Piperacillin) in both aqueous and biological samples.

The electrochemical behavior of the relatively new antibacterial antibiotic Pipril (Piperacillin) at the dropping mercury electrode is investigated using both direct current polarography (DCP) and differential pulse polarography (DPP). At the hanging mercury electrode (HMDE), the reduction mechanism has been elucidated using cyclic voltammetric technique in the pH range from 2 to 10. The effect of some metal ions, e.g. Cu(II) and Pb(II) has been also tested. Determination of the drug using adsorptive stripping analysis was assessed in both aqueous and urine samples. The effect of the different experimental parameters affecting the drug determination, e.g. pH, supporting electrolyte nature, accumulation potential, accumulation time and other operational parameters are also mentioned. Detection limits of 5 x 10(-9) and 1 x 10(-8)M Pipril in aqueous and urine samples, respectively, are achieved.

Anodic adsorptive stripping voltammetric determination of the anesthetic drug: methohexital sodium.

Methohexital (MS) determination is based on the formation of insoluble mercury salt on a hanging mercury drop electrode after preaccumulation by adsorption. This property was exploited in developing a highly sensitive stripping voltammetric procedure for the determination of the drug. The anodic current of adsorbed compound is measured by linear sweep anodic stripping voltammetry (LSASV), preceded by a period of preconcentration. The effect of various parameters such as supporting electrolyte composition, pH, initial potential, scan rate, accumulation time and ionic strength are discussed to characterize the interfacial and redox behavior. The detection limit was found to be 2x10(-7) M (56.8 ppb) with 180-s accumulation time. The interference of some amino acids, ascorbic acid and some metal ions was investigated. The application of this method was tested in the determination of methohexital in spiked urine samples. The precision of the method is satisfactory with a relative standard deviation of 2.5%.