Abdalla M. Abulkibash

Differential electrolytic potentiometric titration method for the determination of ciprofloxacin in drug formulations

A simple and rapid differential electrolytic potentiometric titration method for the determination of ciprofloxacin was developed. The work is based on the fast complexation reaction between iron(III) and ciprofloxacin in a ratio of 1:3, respectively, in sulfuric acid media of 0.09 mol dm(-3). Among the electrodes tested silver amalgam electrodes were found to be a suitable indicating system. By applying a current density of 0.5 muA cm(-2) to these electrodes and using iron(III) solution of 0.097 mol dm(-3) as a titrant, normal titration curves were obtained. The method was successfully applied for the determination of ciprofloxacin in drug formulations as low as 4.0 ppm.

Chemiluminescence assay of promethazine hydrochloride using acidic permanganate employing flow injection mode operated with syringe and peristaltic pumps

For the first time, promethazine hydrochloride chemiluminescence emission was monitored. The paper describes a new, specific and highly sensitive flow injection (FI) method for the determination of promethazine hydrochloride using both a peristaltic and a syringe pump. The method was based on the chemiluminescence emission intensity produced as a result of its oxidation reaction with permanganate in sulfuric acid medium. Reaction variables were thoroughly investigated employing chemometrical methods with few number of experiments. The optimum system and chemical conditions were 2.1519x10(-4) mol l(-1) permanganate in 0.01 mol l(-1) sulfuric acid when operating the peristaltic pump at a flow rate of 45 mul s(-1) and injecting the drug by a syringe pump operated at a speed of 40 mul s(-1). The method was found to be applicable in the concentration range of promethazine hydrochloride between 1.558x10(-5) and 1.8697x10(-3) mol l(-1) with a linear calibration plot of 0.992 correlation coefficient and the following equation: I=92.74+0.08048C. The method adopted proved to be highly suitable for the assay of promethazine hydrochloride in drug formulations without fear of interferences in dosage form.

The depletion of dibenzyl disulfide from a mineral transformer insulating oil

This study examines the kinetics of the net depletion of dibenzyl disulfide (DBDS) from its solution in mineral insulating oil due to copper corrosion at elevated temperatures in power transformers. The concentration of DBDS is determined using liquid-liquid extraction followed by GC detection. Measurements, at 24 h intervals, up to 168 h, show that the depletion of DBDS from its solutions in mineral insulating oil at 150 °C and initial concentrations of 3.00, 6.00, 9.00, 12.00 and 15.00 mg L-1 is very slight compared to identical measurements in the presence of copper strips in the mineral oil. The analysis of the kinetic data reflects the complexity of the corrosion process and its occurrence at a concentration as low as 1 mg L-1 which is much lower than what has been previously believed. Measurements on solutions at initial DBDS concentrations of 150 mg L-1 indicate that even when the insulation oil matrix is in contact with copper strips the corrosion does not occur to any measurable extent below 100 °C and starts to speed up appreciably only beyond 125 °C. From data at 100, 125 and 150 °C an energy of activation equal to 123 kJ mol-1 is estimated.

Rapid inexpensive assay method for verapamil by spectrophotometric sequential injection analysis.

Sequential injection analysis (SIA) technique with a miniaturized fibre optic spectrophotometry was exploited to optimize and validate a new method for the assay of verapamil in pharmaceutical formulations. The reduction of acidified permanganate by verapamil was spectrophotometrically detected at 546 nm. The 2(3) full-factorial design was adopted for screening the effect of conditions controlling the proposed method, and accordingly for the purpose of optimization. The remarkable advantages of the method are high rapidity (sample frequency was 10.6 samples/h), saving in reagents and sample (total consumed volume was 190 µl) and better safety for the environment (total waste production volume was 2140 µl). Additionally, the method was selective in the presence of excipients usually found in tablet and injection formulations. The average of recovery in synthetic samples as well as dosage forms was 98.8-103.0%. The obtained results were realized by the British Pharmacopoeia method and comparable results were obtained.

Cadmium removal by activated carbon, carbon nanotubes, carbon nanofibers, and carbon fly ash: a comparative study

AbstractFour types of carbonaceous adsorbent materials were applied for the removal of cadmium ions from water. These materials include fly ash (FA), activated carbon (AC), carbon nanofibers (CNFs), and carbon nanotubes (CNTs). The adsorption mechanisms and the kinetics of cadmium (II) removal from water were investigated. The effects of pH, the adsorbent dosage, the contact time, and the agitation speed on the removal process were studied and optimized. The four carbon adsorbents were characterized by field emission scanning electron microscopy and transmission electron microscopy. Adsorption isotherms were used to find the model of the adsorption behavior and to calculate the percentage removal. A 95% removal was obtained by using FA at pH 7, a dosage of 50 mg, a contact time of two hours, and an agitation speed of 150 rpm. In case of CNTs, CNFs, and AC, the percentage removals were found to be 27, 34, and 38%, respectively. The experimental data of the four-based carbon adsorbents were well fitted with...

Simultaneous liquid–liquid extraction of dibenzyl disulfide, 2,6‐di‐tert‐butyl‐p‐cresol, and 1,2,3‐benzotriazole from power transformer oil prior to GC and HPLC determination

2,6-Di-tert-butyl-p-cresol (DBPC), dibenzyl disulfide (DBDS), and 1,2,3-benzotriazole (BTA) are additives that may be found concomitantly in the oil matrix of power transformer. DBPC and DBDS act as antioxidants while, BTA is a corrosion inhibitor that protects copper conductors inside the transformer unit from corrosion. A powerful analytical method is, therefore, required to determine these additives at trace levels in the transformer oil. This work describes a unique single liquid-liquid extraction pretreatment step prior to the determination of the components by gas chromatography (GC) and high-performance liquid chromatography (HPLC) techniques. The optimum volume ratio used in the pretreatment step was determined as 5:2:5 for mineral oil/n-hexane/acetonitrile, respectively. Relatively, the method is simple and quick with a minimal use of solvents. Analytical results indicate that the method is relatively sensitive, accurate, and precise for each of the three components in fresh and used mineral oil. The calibration curves for the three components demonstrate a significant increase in sensitivities. Detection limits found were, 100 mg L(-1) (0.01% w/v), 0.80 mg L(-1) , and 2.04 mg L(-1) for DBPC, DBDS, and BTA, respectively. The Students t values determined at 95% confidence level indicate that there is no significant difference between the experimental means obtained by this method and the standard method for each component.

Assessment of dibenzyl disulfide and other oxidation inhibitors in transformer mineral oils

In recent years some unexpected operational failures of power transformers were attributed to the presence of the undeclared dibenzyl disulfide (DBDS) antioxidant in mineral insulating oils. This study examines the characteristics of DBDS and other antioxidants dissolved in a mineral oil. Acidities as neutralization numbers, interfacial tension values and depletion rates were obtained at 100°C for solutions of the antioxidants 2,6-di-tert-butyl-p-cresol (DBPC), 2,6-di-tert-butyl-phenol (DBP), dibenzyl disulfide (DBDS), 2-tert-butyl-p-cresol (2-t-BPC), Nphenyl- 1-naphthylamine, 1,2,3-Benzotriazol (BTA) and methylated-BTA in transformer mineral oil that have been exposed to an accelerated aging process involving flow of oxygen through them at a rate of 1.0 L h-1 over intervals of 24, 48, 72, 96 and 120 hours. The results show that the excellent antioxidant characteristics obtained for DBDS are lost when a copper plate is placed in the mineral oil sample. This is attributable to sulfur corrosion. The results also suggest that DBPC is most suited for use as an antioxidant in transformer mineral oil with DBP a close second. The higher depletion rates encountered for 2-t-BPC and N-phenyl-1- naphthylamine make them less suitable antioxidants. The lower effectiveness of 2-t-BPC as an antioxidant relative to DBPC and DBP may be attributed to the lesser steric hindrance of its - OH group. The results for BTA and methylated-BTA and their higher depletion rates indicate that they would not be suitable antioxidants.

Bromate removal from water using doped iron nanoparticles on multiwalled carbon nanotubes (CNTS)

The raw carbon nanotubes (CNTs) were prepared by the floating catalyst chemical vapor deposition method. The raw carbon nanotubes were functionalized, impregnated with iron nanoparticles, and characterized using high resolution transmission electron microscopy (HRTEM), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and thermogravimetric analysis (TGA). The three types of these multiwalled carbon nanotubes were applied as adsorbents for the removal of bromate from drinking water. The effects of the pH, the concentration of BrO3- anion, the adsorbent dose, the contact time, and the coanions on the adsorption process have been investigated. The results concluded that the highest adsorption capacities were 0.3460 and 0.3220mg/g through using CNTs-Fe and raw CNTs, respectively, at the same conditions. The results showed that the CNTs-Fe gives higher adsorption capacity compared with the raw CNTs and the functionalized CNTs. The presence of nitrate (NO3-) in the solution decreases the adsorption capacity of all CNTs compared with chloride (Cl-) associated with pH adjustment caused by nitric acid or hydrochloric acid, respectively. However, the adsorption of all MWNCTs types increases as the pH of solution decreases.

Portable system of programmable syringe pump with potentiometer for determination of promethazine in pharmaceutical applications

A simple and fast-automated method was developed and validated for the assay of promethazine hydrochloride in pharmaceutical formulations, based on the oxidation of promethazine by cerium in an acidic medium. A portable system, consisting of a programmable syringe pump connected to a potentiometer, was constructed. The developed change in potential during promethazine oxidation was monitored. The related optimum working conditions, such as supporting electrolyte concentration, cerium(IV) concentration and flow rate were optimized. The proposed method was successfully applied to pharmaceutical samples as well as synthetic ones. The obtained results were realized by the official British pharmacopoeia (BP) method and comparable results were obtained. The obtained t-value indicates no significant differences between the results of the proposed and BP methods, with the advantages of the proposed method being simple, sensitive and cost effective.

The minimum concentration of 1,2,3-benzotriazol to suppress sulfur corrosion of copper windings by DBDS in mineral transformer oils

The incubation criterion of the 62535 standard procedure of the International Electrochemical Commission (IEC) was modified to obtain the depletion profiles for different concentrations of each of 1,2,3-benzotriazol (BTA) and dibenzyl disulfide (DBDS) when both are present in a mineral oil matrix. Measurements on BTA concentrations ranging from 0 to of 70 mg L-1 show that its depletion profile after incubation for 72 h, at room temperature, and at 150°C in the presence and absence of a copper strip, is the same irrespective of the DBDS concentration. Similar measurements on DBDS at concentrations ranging from 10 to 300 mg L-1 show that identical depletion profiles are obtained as long as the BTA concentration is maintained in excess of 5 mg L-1. The results show that a minimum BTA concentration of 5 mg L-1 is needed to make the copper windings in contact with the mineral oil passive and in turn suppress their sulfur corrosion by DBDS.