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
A.Merey, H., M. S. Abd-Elmonem, H. N. Nazlawy, and H. E. Zaazaa, "Spectrophotometric Methods for Simultaneous Determination of Oxytetracycline HCl and Flunixin Meglumine in Their Veterinary Pharmaceutical Formulation", Journal of Analytical Methods in Chemistry, vol. https://doi.org/10.1155/2017/2321572, 2017.
Merey, H. A., N. K. Ramadan, S. S. Diab, and A. A. Moustafa, "Validated Spectrophotometric Methods for Simultaneous Determination of Lercanidipine HCl and Enalapril Maleate in their Binary Mixture", Der Pharma Chemica, vol. 9, issue 16, pp. 33-41, 2017. sherine.pdf
Elzanfaly, E. S., and H. A. Merey, "A Liquid Chromatography/Tandem Mass Spectrometric Method for Determination of Captopril in Human Plasma: Application to a Bioequivalence Study", Journal of Applied Pharmaceutical Science, vol. 7, issue 2, pp. 8-15, 2017. Abstract

A simple, rapid and sensitive ultra-performance liquid chromatography/positive ion electrospray tandem mass

spectrometric method was developed and validated for the quantification of captopril in human plasma.

Following plasma protein precipitation, the analyte and internal standard Rosuvastatin were separated by ultra-
performance liquid chromatography using a gradient mode mobile phase on a reversed-phase column and

analyzed by mass spectrometry in the multiple reaction monitoring mode (MRM) using the respective [MRH]R

ions, m/z 218.09/116.16 for captopril and m/z 482.2/ 258.17 for the internal standard. The method exhibited a

linear dynamic range of 10–2000 ng/mL for captopril in human plasma. The lower limit of quantification

was 10 ng/mL with a relative standard deviation of less than 6%. Acceptable precision and accuracy were

obtained for concentrations over the standard curve range. A total run time of 3 minutes for each sample made it

possible to analyze more than 20 human plasma samples per one hour. The validated method has been

successfully applied to analyze human plasma samples in a bioequivalence study of captopril after oral

administration of 50 mg captopril tablet to 24 healthy subjects.

Merey, H. A., "Simple spectrophotometric methods for the simultaneous determination of antipyrine and benzocaine", Bulletin of Faculty of Pharmacy, Cairo University, vol. 54, pp. 181-189, 2016. Abstract

Antipyrine and benzocaine are formulated together for the treatment of ear inflammation
and to relieve pain. Four spectrophotometric methods were developed for the simultaneous
determination of antipyrine (AN) and benzocaine (BE) in their combined dosage form. Method
A depends on applying dual wavelength method where antipyrine was determined by measuring
the absorbance at 254.1 and 309.1 nm (corresponding to zero difference of benzocaine), while the
absorbance difference at 230.1 and 263.5 nm (corresponding to zero difference of antipyrine) was
selected for benzocaine determination in the laboratory prepared spectrum. Method B depends
on measuring the peak amplitude of first derivative at 305 nm for calculating benzocaine concentration
then the total concentration of both drugs was determined using isoabsorptive point at
257.4 nm (antipyrine concentration was then calculated by subtraction). Method C is based on measuring
the peak difference of the ratio spectra at Dp (239.1–285 nm) and Dp (301.4–250 nm) for the
determination of antipyrine and benzocaine, respectively. Method D depends on measuring peak to
peak amplitude of the first derivative of ratio spectra at (234.5 + 244.2 nm) and peak amplitude at
295.5 nm for the determination of antipyrine and benzocaine, respectively. The proposed methods
were validated and applied for the analysis of antipyrine and benzocaine in their laboratory prepared
mixtures and pharmaceutical formulation. Statistical comparison between the results of
the proposed methods and those of the reported methods showed no significant difference.

Merey, H. A., S. S. El-Mosallamy, N. Y. Hassan, and B. A. El-Zeany, "Simultaneous determination of Fluticasone propionate and Azelastine hydrochloride in the presence of pharmaceutical dosage form additives", Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 160, pp. 50-57, 2016. Abstract

Fluticasone propionate (FLU) and Azelastine hydrochloride (AZE) are co-formulated with phenylethyl alcohol
(PEA) and Benzalkonium chloride (BENZ) (as preservatives) in pharmaceutical dosage form for treatment of seasonal
allergies. Different spectrophotometric methods were used for the simultaneous determination of cited
drugs in the dosage form. Direct spectrophotometric method was used for determining of AZE, while Derivative
of double divisor of ratio spectra (DD-RS), Ratio subtraction coupled with ratio difference method (RS-RD) and
Mean centering of the ratio spectra (MCR) are used for the determination of FLU. The linearity of the proposed
methods was investigated in the range of 5.00–40.00 and 5.00–80.00 μg/mL for FLU and AZE, respectively. The
specificity of the developed methods was investigated by analyzing laboratory prepared mixtures containing different
ratios of cited drugs in addition to PEA and their 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 official or the reported method for FLU or AZE, respectively showing no significant difference
with respect to accuracy and precision at p = 0.05.