Elmasry, M. S., M. A. Hasan, W. S. Hassan, H. A. Merey, and I. M. Nour, "Flourimetric study on antidiabetic combined drugs; empagliflozin and linagliptin in their pharmaceutical formulation and human plasma", Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 248, pp. 119258, 2021.
Alamein, A. A. A. M., H. A. Merey, R. E. A. Kalla, and A. E. E. Gendy, "Validated Spectrophotometric Methods for Simultaneous Determination of Sulphadoxine and trimethoprim in a Veterinary Pharmaceutical Dosage Form", Research J. Pharm. and Tech. , vol. 13, issue 11, pp. 5151-5157, 2020.
H. A. Merey, N. K.Ramadan, S. S. Diab, and A. A. Moustafa, "Green spectrophotometric methods for the determination of a binary mixture of lidocaine hydrochloride and cetylpyridinium chloride in the presence of dimethylaniline", Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 242 , pp. 118743, 2020. Abstract

Three green, simple, precise, accurate and sensitive spectrophotometric methods were developed for the determination
of a binary mixture of lidocaine hydrochloride (LDC) and cetylpyridinium chloride (CPC) in the presence
of dimethylaniline (DMA). In the three methods, the interference of DMA spectrum is eliminated using
the ratio subtraction method. Method (A) depended on determining LDC and CPC by measuring the first derivative
of the ratio spectra (1DD) at 271.0 and 268.4 nm, respectively. Method (B) was the ratio difference (RD),
based on dividing the absorption spectrum of the binary mixture by a standard spectrum of CPC or LDC, then
measuring the amplitude difference of the ratio spectra (ΔP) between 231.2 and 240.0 nm for LDC and between
242.8 and 258.0 nm for CPC. Method (C) based on the application of dual wavelength coupled with the
isoabsorptive point method. This was achieved by measuring the absorbance difference (ΔA) between 243.0
and 268.6 nm for the determination of LDC, followed by application of isoabsorptive point method comprised
ofmeasurement the total content of the mixture of LDC and CPC at their isoabsorptive point at 240.0nm. The content
of CPCwas obtained by subtraction. The specificity of the developed methods was investigated by analyzing
laboratory prepared mixtures containing different ratios of LDC and CPC in presence of DMA. The proposed
methods displayed useful analytical characteristics for the determination of LDC and CPC in bulk powder and
their combined dosage form. The obtained results were statistically comparedwith those obtained by the official
methods, showing no significant difference with respect to accuracy and precision.

H. A. Merey, S. S. El-Mosallamy, N. Y. Hassan, and B. A. El-Zeany, "Green monitoring of bromhexine oxidative degradation kinetics", Microchemical Journal, vol. 152, pp. 104378, 2020. Abstract

Kinetics studies are important in quality control to assure the safety and efficacy of the pharmaceutical compounds.
Recently, potentiometric ion-selective electrodes (ISEs) breakthrough kinetics study due to their ability
to provide real-time measurements which meet “green analytical chemistry” (GAC) principles. A polyvinyl
chloride (PVC) matrix membrane was fabricated to monitor bromhexine (BR) oxidative degradation kinetics
using tetraphenylborate as a cation exchanger. At-line monitoring of the oxidative degradation kinetics of BR was
performed; by continuous measuring the decrease in the sensor potential over time. So a real-time observation
and a continuous profile were obtained for the oxidation of BR under various H2O2 concentrations and temperature.
This kinetic study determines the oxidation activation energy that was 6.4 kcal mol−1. To expand the
application of this sensor, BR was determined in bulk powder and dosage form in the presence of both coformulated
drug (acefylline piperazine) and dosage form additives. The proposed sensor had been characterized
according to IUPAC recommendations and a linear dynamic range was 5×10−6 to 1×10−3M and other sensor
parameters had been calculated.

H. A. Merey, S. S. El-Mosallamy, N. Y. Hassan, and B. A. El-Zeany, "Validated eco--friendly spectrophotometric methods for the determination of acefylline piperazine and bromhexine hydrochloride in the presence of dosage form additives", Journal of Applied Spectroscopy, vol. 87, issue 1, pp. 159-168, 2020.
Merey, H. A., S. S. El-Mosallamy, N. Y. Hassan, and B. A. El-Zeany, "Validated Chromatographic Methods for Simultaneous Determination of Calcipotriol Monohydrate and Betamethasone Dipropionate in the Presence of Two Dosage Form Additives.", Journal of chromatographic science, vol. 57, issue 4, pp. 305-311, 2019. Abstract

Two chromatographic methods were developed, optimized and validated for simultaneous determination of calcipotriol monohydrate (CPM) and betamethasone dipropionate (BMD) in the presence of two dosage form additives named; butylated hydroxytoluene (BHT) and alpha-tocopherol (TOCO). The proposed methods were accurate, sensitive and specific. The first method based on using aluminum thin-layer chromatographic plates precoated with silica gel GF254 as a stationary phase and chloroform-ethyl acetate-toluene (5:5:3, by volume) as a developing system. This was followed by densitometric measurement of the separated bands at 264 nm. Whereas the second method is RP-HPLC where OnyxMonolithic C18® column was used with a gradient profile using methanol, water and acetic acid at flow rate 2.0 mL min-1. Detection was carried out at 264 nm. The methods were validated according to ICH guidelines. The specificity of the developed methods was investigated by analyzing the pharmaceutical dosage form. The validity of the proposed methods was assessed using the standard addition technique. The obtained results were statistically compared with those obtained by the official methods, showing no significant difference with respect to accuracy and precision at P = 0.05.

Merey, H. A., N. K. Ramadan, S. S. Diab, and A. A. Moustafa, "Chromatographic methods for the simultaneous determination of binary mixture of Saxagliptin HCl and Metformin HCl", Bulletin of Faculty of Pharmacy, Cairo University, vol. 55 , pp. 311-317, 2017. paper.pdf
Mohamed, M. A., S. A. Atty, H. A. Merey, T. A. Fattah, C. W. Foster, and C. E. Banks, "Titanium nanoparticles (TiO2) / Graphene oxide nanosheets (GO): an electrochemical sensing platform for the sensitive and simultaneous determination of benzocaine in the presence of antipyrine", Analyst, vol. 142, issue 19, pp. 3674-3679, 2017.
Merey, H. A., and S. A. Atty, "Eco-friendly stability-indicating potentiometric method for the determination of ropinirole hydrochloride", Analytical and Bioanalytical Electrochemistry, vol. 9, issue (8), pp. 1044-1056, 2017. paper.pdf
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