Nazlawya, H. N., H. E. Zaazaa, H. A. Merey, and S. A.Attya, "Green voltammetric nano scaled determination of toldimfos and its residues in cattle meat and milk in presence of its toxic metabolite and Co-administered vitamin C", Sustainable Chemistry and Pharmacy , vol. 31, pp. 100906, 2023.
Farag, M. M., H. B. El-Nassan, H. A. Merey, B. M. Eltanany, M. M. Galal, W. Wadie, D. M. El-Tanbouly, M. A. Khattab, L. A. Rashed, and A. N. ElMeshad, "Comparative pharmacodynamic study delineating the efficacy of amantadine loaded nano-emulsified organogel via intranasal versus transdermal route in rotenone-induced Parkinson’s disease rat model", Journal of Drug Delivery Science and Technology, vol. 86 , pp. 104765, 2023.
Farag, M. M., H. B. El-Nassan, H. A. Merey, B. M. Eltanany, M. M. Galal, W. Wadie, D. M. El-Tanbouly, M. A. Khattab, L. A. Rashed, and A. N. ElMeshad, Comparative pharmacodynamic study delineating the efficacy of amantadine loaded nano-emulsified organogel via intranasal versus transdermal route in rotenone-induced Parkinson’s disease rat model, .
Elmasry, M. S., W. S. Hassan, H. A. Merey, and I. M. Nour, "Earth-friendly micellar UPLC technique for determination of four hypoglycemic drugs in different pharmaceutical dosage forms and spiked human plasma", BMC Chemistry, vol. 17, issue 74, pp. 1-11, 2023. Abstractesraa.pdf

A novel, sensitive, and green micellar UPLC method was proposed and validated for the simultaneous
determination of four hypoglycemic agents used in type II diabetes mellitus treatment namely, pioglitazone,
alogliptin, glimepiride, and vildagliptin. The developed UPLC method was successfully applied for quantitative
analysis of these drugs in bulk, in pharmaceutical formulations, and in spiked human plasma. Chromatographic
separation was carried out on a Kinetex® 1.7 μm XB-C18 100 Å (50 × 2.1 mm) column, using a degassed and filtered
mixture of (0.1 M SDS- 0.3% triethyl amine- 0.1% phosphoric acid (pH 6)) and n-propanol (85:15 v/v), at a flow rate
of 0.2 mL/min. The experimental conditions of the suggested method were well investigated and optimized. The
newly developed micellar UPLC method is capable of determining different dosage forms at the same time with
the same solvents, saving time and effort. The method was found to be efficiently applicable in spiked human
plasma and could be extended to study the pharmacokinetics of the cited drugs in real human plasma samples.
The greenness of the developed method was evaluated by applying the Eco-scale scoring tool, which verified the
excellent greenness of the analytical method.

Ramadan, N. K., H. A. Merey, S. S. Diab, and A. A. Moustafa, "In-Line Green Potentiometric Monitoring of Dissolution Behavior of Losartan Potassium Versus Pharmacopeial Methods: A Comparative Study", Analytical Chemistry letters, vol. 12, 2022. Abstract

Green electro-analytical method was developed and validated for quantitative determination and monitoring of the dissolution behavior of Losartan potassium tablets by in-line potentiometric measurement system with no need for pre-treatment or derivatization of the sample. A sensor was fabricated for in-line determination of Losartan potassium LOS in its dissolution medium utilizing polyvinyl chloride (PVC) based membrane and nitrophenyl octyl ether (NPOE) as a plasticizer. Tetraheptyl ammonium bromide (THAB) was employed as anion exchanger for the first sensor, while cetyltrimethylammonium bromide (CTAB) was used in the second sensor. The proposed method showed fast, stable near Nernstian responses across a relatively wide LOS concentration range (1.0 × 10-5 to 1.0 × 10-2 mol/L) in the case of THAB-based sensor while LOS concentration range was (1.0 x 10-4 - 1.0 x 10-2 mol/L) in case of CTAB-based sensor. The dissolution method
was developed according to FDA regulations using USP apparatus II, 50 rpm rotation speed, at 37.0 ± 0.5°C and 900 mL of deareated double distilled water as the dissolution medium. Dissolution profile was generated over 45 min and compared to those obtained by the official spectrophotometric and HPLC methods. The developed method can be efficiently applied as benchtop real-time in-process analysis of LOS concentration. Greenness assessment using Analytical Eco-scale, National Environmental Method Index (NEMI), Green Analytical Procedure Index (GAPI) and Analytical Greenness (AGREE) calculator was conducted to evaluate and compare the proposed method with the official ones.

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. Abstract

Empagliflozin and linagliptin are newly approved FDA combination that used for the treatment of type 2 diabetes mellitus (T2DM) under trade name Glxambi. Two spectroflourimetric methods were developed for simple quantitative determination of empagliflozin and linagliptin in their pharmaceutical formulation and human plasma without need any tedious processing operations. Empagliflozin has a native fluorescence nature, therefore can be directly determined by measuring emission peak at 305 nm after excitation at 234 nm. There is no any interference from linagliptin at this emission wavelength. On the other hand, linagliptin is a very weak florescent compound that needs to react with fluorogenic reagent to be quantitatively determined without any reaction of empagliflozin. So, quantitative analysis of linagliptin was achieved by coupling with NBD-Cl which is an electro active halide reagent (targeting only Linagliptin with no effect on empagliflozin). Dark yellow fluorophore with high fluorescence is a result of this reaction and can be measured at emission wavelength 538 nm after excition at wavelength 469 nm. Experimental conditions of the suggested methods were well checked and optimized. The regression plots were found to be linear over the range of 40-1200 ng/mL and 3-700 ng/mL for empagliflozin and linagliptin, respectively. The obtained results by the suggested methods were statistically compared with those obtained by the reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Elmasry, M. S., W. S. Hassan, H. A. Merey, and I. M. Nour, "Simple mathematical data processing method for the determination of sever overlapped spectra of linagliptin and empagliflozin in their pure forms and pharmaceutical formulation: Fourier self deconvulated method.", Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, vol. 254, pp. 119609, 2021. Abstract

A new and simple spectrophotometric method was developed for the simultaneous determination of a new antidiabetic mixture of linagliptin and empagliflozin namely fourier self deconvulated method. The developed method based on minimal mathematical data processing on the zero order spectrum for solving sever overlapping spectra of the mentioned drugs in their pure forms and pharmaceutical dosage form. The zero order spectra of linagliptin and empagliflozin were deconvulated using Fourier transforms function. The peak amplitudes at 232 nm were selected for linagliptin and at 239 nm for empagliflozin. The constructed calibration graphs were linear over the range (5-30 µg/mL) and (2-12 µg/mL) for empagliflozin and linagliptin, respectively. The adopted method was simple, accurate, precise and validated according to the ICH guidelines.

Ibrahim, H., A. M. Hamdy, H. A. Merey, and A. S. Saad, "Simultaneous Determination of Paracetamol, Propyphenazone and Caffeine in Presence of Paracetamol Impurities Using Dual-Mode Gradient HPLC and TLC Densitometry Methods.", Journal of chromatographic science, vol. 59, issue 2, pp. 140-147, 2021. Abstract

Two chromatographic methods were validated for the determination of the widely prescribed analgesic and antipyretic drug combination of paracetamol (PC) (recently integrated into the supportive treatment of COVID-19), propyphenazone (PZ) and caffeine (CF) in the presence of two PC impurities, namely 4-aminophenol and 4-nitrophenol. A "dual-mode" gradient high-performance liquid chromatography method was developed, where the separation was achieved via "dual-mode" gradient by changing both the ternary mobile phase composition (acetonitrile: methanol: water) and the flow rate. This enables a good resolution within a relatively shorter analysis time. The analysis was realized using Zorbax Eclipse XDB column C18, 5 μm (250 × 4.6 mm) and the UV detector was set at 220 nm. The other method is a thin-layer chromatography densitometry method, where the separation was achieved using a mobile phase composed of chloroform: toluene: ethyl acetate: methanol: acetic acid (6: 6: 1: 2: 0.1, by volume). Densitometric detection was performed at 220 nm on silica gel 60 F254 plates. The developed methods were fully validated as per the ICH guidelines and proved to be accurate, robust, specific and suitable for application as purity indicating methods for routine analysis of PC in pure form or in pharmaceuticals with PZ and CF in quality control laboratories.

Ibrahim, H., A. M. Hamdy, H. A. Merey, and A. S. Saad, "Dual-Mode Gradient HPLC and TLC Densitometry Methods for the Simultaneous Determination of Paracetamol and Methionine in the Presence of Paracetamol Impurities.", Journal of AOAC International, vol. 104, issue 4, pp. 975-982, 2021. Abstract

BACKGROUND: Paracetamol (PC) is one of the most widely used analgesic and antipyretic drugs and has recently been integrated into the supportive therapy of COVID-19. Pharmaceuticals containing methionine (MT) with PC may contribute to avoid hepatotoxicity and eventual PC overdose-dependent death.

OBJECTIVE: The current work purposes to develop and validate two chromatographic methods for the simultaneous determination of MT and PC in the presence of two PC impurities (4-nitrophenol [NP] and 4-aminophenol [AP]).

METHOD: Two chromatographic methods were established and validated according to the International Conference on Harmonization guidelines. The first one was an RP-HPLC/UV method based on applying a "dual-mode" gradient elution. The separation was realized via varying both the composition of the ternary mobile phase (acetonitrile-methanol-water) and its flow rate. This strategy enabled a relatively rapid analysis with a satisfactory resolution, although the investigated compounds exhibit a significant difference in lipophilicity. The second one relied on TLC-densitometry, where the optimum separation was realized using a quaternary mobile phase system composed of butanol-dioxane-toluene-methanol (8:2.5:3.5:0.3, by volume). Both methods were monitored at 220 nm.

RESULTS: The developed methods were proven to be robust, accurate, specific, and appropriate for the routine analysis of PC in its pure form or in pharmaceutical formulations with MT in quality control laboratories.

CONCLUSIONS: The corresponding methods are suitable to determine MT and PC in the presence of PC impurities.

HIGHLIGHTS: The study achieves the analysis of MT and PC in the presence of PC impurities via the application of HPLC and TLC-densitometry methods.

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