Eman Yossri Frag

Utility of π-acceptor reagents for spectrophotometric determination of sulphonamide drugs via charge-transfer complex formation

A simple, sensitive and accurate spectrophotometric method for the determination of sulphonamides (sulphamethoxazole (SMZ), sulphaguanidine (SGD), sulphaquinoxaline sodium (SQX), sulphametrole (SMR), and sulphadimidine sodium (SDD)) has been developed. The charge-transfer reactions between sulphonamides as n-electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, p-CLA) as π-acceptors resulting in highly coloured complexes were studied. Experimental conditions for these CT reactions were carefully optimised. Beer’s law is valid over the concentration ranges from 4–280 µg mL−1, 4–260 µg mL−1, 4–200 µg mL−1, and 4–200 µg mL−1 of SMZ, SGD, SQX, and SDD using DDQ reagent, respectively. While the calibration curves are linear in the concentration ranges from 4–180 µg mL−1, 4–80 µg mL−1, 4–60 µg mL−1, 4–180 µg mL−1, and 4–60 µg mL−1 of SMZ, SGD, SQX, SMR, and SDD, respectively, using TCNQ reagent and from 4–380 µg mL−1 and 4–300 µg mL−1 of SQX and SDD, respectively, using p-CLA reagent, respectively. Different analytical parameters, namely molar absorptivity (ε), standard deviation, relative standard deviation, correlation coefficient, limit of detection, and limit of quantification, were calculated. The results obtained by the proposed methods are in good agreement with those obtained by the official method as indicated by the percent recovery values.

Coupling reaction and complex formation for the spectrophotometric determination of physiologically active catecholamines in bulk, pharmaceutical preparations and urine samples of schizophrenic patients

A simple and sensitive spectrophotometric method for the determination of three catecholamines namely dopamine hydrochloride (DO.HCl), dobutamine hydrochloride (DOB.HCl) and vanillymandelic acid (VMA), in both pure form or in their commercially available pharmaceutical formulations or urine samples of schizopherinic patients is described. The method is based on the reaction of diazotized 4-aminoantipyrine (4-AAP) with catecholamines in a basic medium (pH = 10-11) to yield pink-coloured products having absorption maxima at 500, 505 and 480 nm for DO.HCl, VMA and DOB.HCl, respectively. Before carrying out Beers Law, different experimental conditions, such as time, temperature, sequence of addition, and pH are optimized. The coloured species obeyed Beers Law in the range of 47.4-417.2, 59.45-445.9 and 67.57-405.4 mg/L for DO.HCl, VMA and DOB.HCl, respectively. The molar absorptivity values as obtained from Beers Law data were found to be 2.979 x 10(4), 4.39 x 10(4) and 1.036 x 10(4) L mol(-1) cm(-1), while Sandells sensitivity values were observed to be 3 x 10(-3), 4.4 x 10(-3) and 1.3 x 10(-3) microg cm(2-) for DO.HCl, VMA and DOB.HCl, respectively. Common excipients did not interfere with the proposed method. The results of the proposed method compare favourably with those of official methods. The proposed method offers simplicity, reliability, rapidity, and accuracy compared to the existing methods.

Application of carbon sensors for potentiometric determination of copper(II) in water and biological fluids of Wilson disease patients. Studying the surface reaction using SEM, EDX, IR and DFT

The performance characteristics of a new selective and sensitive modified screen printed electrode (MSPE; electrode I) and carbon paste electrode (MCPE; electrode II) based on 2-N, N-dimethylcarbamimidoyl (metformin) as modifier for the potentiometric determination of copper (II) in water sample, serum and urine samples of Wilson disease patients have been optimized. The chemical reaction which happens between Cu (II) and the modifier on the surface of the sensors was investigated with scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), IR spectra measurement and computational calculations at DFT/B3LYP. The sensors showed perfect potentiometric response for Cu (II) over concentration range of 1.0 × 10-6 - 1.0 × 10-2 and 1.0 × 10-6 - 5.0 × 10-2 mol L-1 with a detection limit of 1.0 × 10-6 mol L-1with divalent slope value 30.2 and 31.8 mV decade-1 over the pH range of 2-6 for MCPE and MSPE, respectively. MSPE was stable with repeatable potential over period of 37 days and exhibits fast response time of 6 and 10 s for MSPE and MCPE, respectively. Also, these sensors exhibited good selectivity towards Cu(II) with respect to other metal ions and have higher antibacterial activity against Staphylococcus aureus as Gram-positive bacteria and Escherichia coli as Gram-negative bacteria. The obtained results using the sensors were in agreement with those obtained using the reported method.

Kinetic study of the alkaline degradation of imidapril hydrochloride using a validated stability indicating HPLC method

An aqueous alkaline degradation study was performed for imidapril hydrochloride (IMD) drug in the presence of its degradation products and an isocratic stability indicating method was presented using a HPLC technique. The separations were performed using an ACE Generix 5C8, 150 × 4.6 mm column and a mobile phase consisting of buffer solution (0.1 M potassium dihydrogen phosphate and 0.02 M tetra-N-butyl ammonium hydrogen sulphate of pH = 4.5 with 1 N HCl) and acetonitrile 60 : 40 (v/v). The wavelength of the detector was adjusted at 210 nm. The method showed high sensitivity concerning accuracy, precision, linearity and specificity within the acceptable range from 0.1 to 100 μg mL−1 and the limit of quantification was found to be 0.0211 μg mL−1 for IMD. The proposed method was used to determine the drug in its pharmaceutical formulation and to investigate the degradation kinetics of the drugs alkaline-stressed sample. The reactions were found to follow a first-order reaction. The activation energy could also be estimated. The optimized stability indicating HPLC method was validated according to ICH guidelines.