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.

Melatonin charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone: Molecular structure, DFT studies, thermal analyses, evaluation of biological activity and utility for determination of melatonin in pure and dosage forms.

A simple, accurate and fast spectrophotometric method for the quantitative determination of melatonin (ML) drug in its pure and pharmaceutical forms was developed based on the formation of its charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electron acceptor. The different conditions for this method were optimized accurately. The Lambert-Beer's law was found to be valid over the concentration range of 4-100µgmL-1 ML. The solid form of the CT complex was structurally characterized by means of different spectral methods. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were carried out. The different quantum chemical parameters of the CT complex were calculated. Thermal properties of the CT complex and its kinetic thermodynamic parameters were studied, as well as its antimicrobial and antifungal activities were investigated. Molecular docking studies were performed to predict the binding modes of the CT complex components towards E. coli bacterial RNA and the receptor of breast cancer mutant oxidoreductase.

In situ modified screen printed and carbon paste ion selective electrodes for potentiometric determination of naphazoline hydrochloride in its formulation.

The construction and performance characteristics of new sensitive and selective in situ modified screen printed (ISPE) and carbon paste (ICPE) electrodes for determination of naphazoline hydrochloride (NPZ-HCl) have been developed. The electrodes under investigation show potentiometric response for NPZ-HCl in the concentration range from 7.0×10-7 to 1.0×10-2 M at 25 °C and the electrode response is independent of pH in the range of 3.1-7.9. These sensors have slope values of 59.7±0.6 and 59.2±0.2 mV decade-1 with detection limit values of 5.6×10-7 and 5.9×10-7 M NPZ-HCl using ISPE and ICPE, respectively. These electrodes show fast response time of 4-7 s and 5-8 s and exhibits lifetimes of 28 and 30 days for ISPE and ICPE, respectively. Selectivity for NPZ-HCl with respect to a number of interfering materials was also investigated. It was found that there is no interference from the investigated inorganic cations, anions, sugars and other pharmaceutical excipients. The proposed sensors were applied for the determination of NPZ-HCl in pharmaceutical formulation using the direct potentiometric method. It showed a mean average recovery of 100.2% and 102.6% for ISPE and ICPE, respectively. The obtained results using the proposed sensors were in good agreement with those obtained using the official method. The proposed sensors show significantly high selectivity, response time, accuracy, precision, limit of detection (LOD) and limit of quantification (LOQ) compared with other proposed methods.