Mahmoud Khodari

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.

Determination of Ag(I) with chemically modified carbon paste electrode based on 2,3-dicyano 1,4-naphthoquinone

The utility of carbon paste modified with 2,3-dicyano 1,4-naphthoquinone (CYNQ) for the voltammetric determination of Ag(I) is demonstrated. The method is based on the formation of Ag(I) complex with CYNQ by accumulation from the aqueous solution to the electrode surface without an applied potential. Using the medium exchange technique, the electrode was transferred to another media followed by linear-scan voltammetric measurements. The reduction peak of the Ag(I)-CYNQ complex was observed at +0.22 V (vs. SCE). The silver response is studied with respect to paste composition, pH of the measurement solution, reproducibility, interference and other variables. A detection limit of 5 x 10(-8)M was obtained and the calibration curve was linear over the range 1 x 10(-6)-8 x 10(-5)M.

Preconcentration and Determination of the Tricyclic Antidepressant Drug - Imipramine at Modified Carbon Paste Electrode

Abstract The accumulation/voltammetric behavior of the tricyclic antidepressant imipramine (Imip) was investigated at a fatty acid modified carbon paste electrode This hydrophobic drug accumulated onto the electrode surface, then was stripped by scanning the potential toward the positive direction. The oxidation peak response showed a great enhancement on using the modified electrode over the unmodified one. The peak current was examined with respect to preconcentration time, pH, paste composition, reproducibility, possible interferences and other variables. The response is linear over the range from 0.1 to 8.0 μM (r = 0.9980), after 3 minutes stirring time, using phosphate (0.1 M) pH 9. A detection limit of 0.001 μM was obtained. The method was applied to the pharmaceutical formulation Tofranil and to the biological samples.

Cathodic stripping voltammetric behaviour of nitrofurazone and its determination in pharmaceutical dosage form, urine and serum by linear sweep voltammetry.

The antibacterial drug, nitrofurazone [5-nitro-2furaldehyde semicarbazone] a synthetic nitrofuran derivative, was reported to possess good bacteriostatic and bactericidal properties, has an antibacterial action against a number of Gram-negative and Gram-positive micro-organisms [1,2] and is used for the treatment of burns [3] and trypanosomiasis [4]. In veterinary medicine nitrofurazone is used for the treatment and prophylaxis of coccidiosis in poultry and farm animals, and necrotic enteritis in pigs [1]. The determination of some nitrated heterocyclic compounds containing reduction sites similar to that of nitrofurazone was studied by Vignoli et al. [5] using Brittion–Robinson (BR) buffer pH of between 1.81 and 11.98. Various methods including spectrophotometry [6,7], turbidity [8], colorimetry [9,10], conductimetry [11], paper chromatography [12] and high performance liquid chromatography [13,14] have determined nitrofurazone in its pharmaceutical preparations. A little attention has been paid to the polarographic determination of nitrofurazone [15–18] or to the electrochemical behaviour of this compound [19,20]. A rotating platinum electrode was used to study nitrofurazone by a simple direct current procedure [21–24]. The present work is a continuation of our studies in the field of the determination of the antibacterial drugs using cathodic stripping voltammetry (CSV) at the hanging mercury drop electrode (HMDE) [25]. This technique offers a high senstivity with respect to the other analytical techniques [26]. The aims of this study are to establish the experimental conditions, to investigate the adsorptive voltammetric behaviour of nitrofurazone and to optimize the conditions for determination of the titled compound in pharmaceutical formulations present in urine and serum. * Corresponding author.

Cathodic Stripping Voltammetry of the Antibacterial Drug (Nitrofurantoin)

Abstract Cathodic stripping voltammetry was used to determine the antibacterial drug Nitrofurantoin in phosphate buffer (pH 5.5). The adsorptive peak was observed at −0.173 V vs. Ag/AgCl. The peak response was characterized with respect to pH, preconcetration time, possible interferences, deposition potential, supporting electrolytes and other variables. The obtained results were analyzed and the statistical parameters were calculated. Also the method was applied to determine the mentioned drug in pharmaceutical formulations and urine. The limit of detection was 1 × 10−9 mol dm−3.

Quantification of tiaprofenic acid using voltammetric and spectrophotometric techniques

Two methods for the determination of tiaprofenic acid (Surgam) are described. Direct current polarography and cyclic voltammetry were used to study the reduction behaviour of tiaprofenic acid, whereas direct current stripping voltammetry was applied to the quantitative measurement of the drug in dosage form and in biological media. The spectrophotometric method depends on the determination of the drug after extraction as an ion-association complex with Safranine-T in chloroform at pH 7.4.

Electrochemical behaviour of drugs at lipid modified carbon paste electrodes

Abstract Mixing carbon paste with a charged lipid, in an appropriate ratio, permitted us to prepare a modified electrode whose surface exhibits interesting characteristics of the constituting lipid. Two negatively charged phospholipids have been selected, namely: asolectin and cardiolipin. By investigating the electrooxidation of several drugs which are known to interact strongly with the lipid component of cellular membranes (adriamycin, epirubicin and promethazine) it was possible to demonstrate markedly different behaviour at the lipid modified carbon paste electrode (LMPCE) depending on the pH of the solution. By analysing the results of linear scan, ac and adsorptive voltammetry and by taking into account literature data on drug—membrane interactions, it was possible to postulate a model of the LMCPE interface with thin layers of lipids covering the graphite particles. The differential capacity measurements as a function of time (fixed potential) and in the presence of increasing amounts of drugs enabled us to point out profound increases in the capacity of the LMCPE in the presence of adriamycin and epirubicin. In addition, the more negatively charged the lipids were, the higher was the capacity increase.

Determination of Cadmium in Seawater by Cathodic Stripping Voltammetry of Complexes with 5-Fluorouracil

A reduction current is obtained when an aqueous solution of cadmium and 5-fluorouracil (5-FU) is subjected to linear sweep cathodic stripping voltammetry. This current is attributed to the reduction of cadmium-5-FU complex ions which adsorbed onto the hanging mercury drop electrode. The resulting peak current is characterized with respect to supporting electrolytes, pH, accumulation potential, scan rate, possible interferences and other variables. A linear relationship between the peak current and cadmium concentration was obtained over the range 5 × 10−9–1 × 10−7 mol dm−3 with correlation coefficient of 0.9973. A detection limit of 9.0 × 10−11 mol dm−3 was obtained with standard deviation of 1.9 %. The method was successffuly applied for the determination of cadmium in seawater.

Adsorptive stripping voltammetric determination of uranium with cephradine

Uranium adsorbed with cephradine is reduced on a hanging mercury drop electrode. This property was exploited in developing a highly sensitive stripping voltammetric procedure for the determination of uranium. A detection limit 2 × 10–9 mol l–1(0.5 µg l–1) of uranium ion is obtained with an 180 s accumulation time. Cyclic voltammetry was used to characterize the interfacial and redox behaviour. The effects of various parameters are discussed. Experimental conditions include the use of 5 × 10–6 mol l–1 cephradine in 0.05 mol l–1 sodium perchlorate (pH ≈ 6.5), an accumulation potential of 0.0 V versus SCE and a direct current stripping technique. The response is linear up to 5 × 10–6 mol l–1 uranium and the relative standard deviation at 1 × 10–7 mol l–1 UO2+ is 4.4%. The effect of other metal ions was investigated.

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.