Fekry, R. A., K. M. Kelani, Y. M. Fayez, and M. A. Tantawy, Comparative validated chromatographic methods for the simultaneous determination of caffeine, codeine, paracetamol along with the related compound "p-aminophenol" in tablets, , vol. 35, issue 1, pp. 51 - 59, 2022. AbstractWebsite

This paper presents two validated chromatographic methods, namely thin-layer chromatography (TLC)–densitometry and high-performance liquid chromatography (HPLC), for the simultaneous determination of caffeine (CAF), codeine (COD), paracetamol (PAR) in the presence of p-aminophenol (PAP) in their quaternary mixture. Good separation was achieved by using silica gel as the stationary phase and chloroform‒methanol‒acetone‒ammonia (8:1:2:0.1, V/V) as the mobile phase in the case of TLC–densitometry with retardation factor (RF) values of 0.38 ± 0.02, 0.24 ± 0.02, 0.61 ± 0.02 and 0.46 ± 0.02 for PAR, COD, CAF and PAP, respectively. Zorbax ODS column with mobile phase consisting of 0.1% orthophosphoric acid and acetonitrile (92:8, V/V) was used as stationary and mobile phase for HPLC, respectively, with retention time (tR) values of 1.1, 3.5, 4.6 and 8.5 min for CAF, PAP, COD and PAR, respectively. The two proposed methods were validated as per the International Council for Harmonisation guidelines. Finally, they were successfully applied for determination of the cited drugs in their quaternary mixture and marketed formulation.

Tantawy, M. A., I. A. Wahba, Samah S Saad, and N. K. Ramadan, Stability-Indicating Chromatographic Methods for the Simultaneous Determination of Probenecid and Colchicine in Their Combined Tablet, , vol. 59, issue 10, pp. 956 - 963, 2021/11/01. AbstractWebsite

Two stability-indicating chromatographic methods have been established and validated for concurrent determination of probenecid (PRO), colchicine (COL) along with the degradation product of colchicine (COL deg). PRO and COL were exposed to a stress stability study, which includes acidic, alkaline, oxidative, photolytic and thermal degradations. Chromatographic methods included the use of thin layer chromatography (TLC-densitometry) and high performance liquid chromatography (HPLC). In the first method, separation was achieved by using aluminum TLC plates that were precoated with silica gel G.F254 as the stationary phase and ethyl acetate–methanol–33%ammonia (8:1:1, by volume) as a mobile phase. The obtained chromatograms were scanned at 254 nm. The second method was based on HPLC using a RP- C18 column with isocratic elution. Good separation was obtained through a mobile phase comprised of phosphate buffer pH 5–acetonitrile (70:30, v/v) at a flow rate of 1.0 mL min−1 and ultraviolet detection at 254 nm. Different parameters affecting efficiency of the two methods were studied accurately for optimum separation of the three cited components. The suggested methods were validated according to the International Conference on Harmonization (ICH) guidelines and were applied for bulk powder and commercial tablets.

Tantawy, M. A., I. A. Wahba, Samah S Saad, and N. K. Ramadan, Two Validated Chromatographic Methods for Determination of Ciprofloxacin HCl, One of its Specified Impurities and Fluocinolone Acetonide in Newly Approved Otic Solution, , pp. bmab110, 2021/09/20. AbstractWebsite

Two sensitive, selective and precise chromatographic methods have been established for concomitant quantification of ciprofloxacin HCl (CIP), fluocinolone acetonide (FLU) along with ciprofloxacin impurity A (CIP-imp A). The first method was thin-layer chromatography (TLC-densitometry) where separation was accomplished using TLC silica plates 60 G.F254 as a stationary phase and chloroform–methanol–33%ammonia (4.6:4.4:1, by volume) as a developing system. The obtained plates were scanned at 260 nm over concentration ranges of 1.0–40.0, 0.6–20.0 and 1.0–40.0 μg band−1 for CIP, FLU and CIP-imp A, respectively. The second method was based on high-performance liquid chromatography using a Zorbax ODS column (5 μm, 150 × 4.6 mm i.d.) where adequate separation was achieved through a mobile phase composed of phosphate buffer pH 3.6–acetonitrile (45:55, v/v) at flow rate 1.0 mL min−1 with ultraviolet detection at 254 nm. Linear regressions were obtained in the range of 1.0–40.0 μg mL−1 for CIP, 0.6–20.0 μg mL−1 for FLU and 1.0–40.0 μg mL−1 for CIP-imp A. The suggested methods were validated in compliance with the International Conference on Harmonization guidelines and were successfully applied for determination of CIP and FLU in bulk powder and newly marketed otic solution.

Tantawy, M. A., A. M. Hassan, M. A. Hegazy, and K. M. Kelani, Quality and Stability Profile Assessment of the Recent Antidiabetic Omarigliptin by Using Different Chromatographic Methods, , vol. 59, issue 8, pp. 762 - 769, 2021/09/01. AbstractWebsite

In a contribution to stability profiling of the recent antidiabetic drug, omarigliptin (OMR), two stability-indicating chromatographic methods were developed and validated. Stability profiling was performed for OMR under different stress conditions as acidic, alkaline, oxidative, photolytic and thermal degradations. Structures elucidation to all formed degradation products were identified using IR and mass spectrometry. Thin Layer Chromatography (TLC) and High-Performance Liquid Chromatography (HPLC) were used. In TLC-densitometric method, aluminum TLC plates precoated with silica gel G.F254 were used as stationary phase along with methanol: ethyl acetate: 33% ammonia (2:8:1,v/v/v) as mobile phase. The obtained chromatograms were scanned at 254 nm over concertation range of 5–70 μg band−1 for OMR. The second chromatographic method was an HPLC one with diode array detection and RP-C18 column with isocratic elution. Mobile phase used was composed of phosphate buffer pH 3.5: acetonitrile (80, 20, v/v), delivered at flow rate of 1.0 mL min−1. Diode array detector was adjusted at 230 nm with linearity range of 15–180 μg mL−1 for OMR. Several factors affecting TLC and HPLC efficiency have been carefully studied. The developed methods were validated according to International Conference on Harmonization guidelines and successfully applied for assessment of OMR in bulk powder and tablets.

Tantawy, M. A., E. H. Mohamed, and A. M. Yehia, All solid-state miniaturized potentiometric sensors for flunitrazepam determination in beverages, , vol. 188, issue 6, pp. 192, 2021. AbstractWebsite

Flunitrazepam is one of the frequently used hypnotic drugs to incapacitate victims for sexual assault. Appropriate diagnostic tools should be available to victims regarding the growing concern about “date-rape drugs” and their adverse impact on society. Miniaturized screen-printed potentiometric sensors offer crucial point-of-care devices that alleviate this serious problem. In this study, all solid-state screen-printed potentiometric flunitrazepam sensors have been designed. The paper device was printed with silver and carbon ink. Formation of an aqueous layer in the interface between carbon-conducting material and ion-sensing membrane nevertheless poses low reproducibility in the solid-contact electrodes. Accordingly, poly(3,4-ethylenedioxythiophene) (PEDT) nano-dispersion was applied as a conducting hydrophobic polymer on the electrode surface to curb water accumulation. Conditioning of ion-sensing membrane in the vicinity of reference membrane has been considered carefully using special protocol. Electrochemical characteristics of the proposed PEDT-based sensor were calculated and compared favorably to PEDT-free one. The miniaturized device was successfully used for the determination of flunitrazepam in carbonated soft drinks, energy drink, and malt beverage. Statistical comparison between the proposed sensor and official method revealed no significant difference. Nevertheless, the proposed sensor provides simple and user-friendly diagnostic tool with less equipment for on-site determination of flunitrazepam.

Wadie, M., E. M. Abdel-Moety, M. R. Rezk, and M. A. Tantawy, Eco-friendly chiral HPLC method for determination of alfuzosin enantiomers and solifenacin in their newly pharmaceutical combination: Method optimization via central composite design, , vol. 165, pp. 106095, 2021. AbstractWebsite

The high abundance and advantages of polysaccharides make them among the most widely used chiral stationary phases in liquid chromatography. However, extended analysis time and consumption of toxic organic solvents, associated with traditional columns, remain the main stumbling blocks of such methods’ sustainability. A new green chiral HPLC-separation, with just 0.45 mL ethanol in mobile phase per run utilizing a 50-mm column as a stationary phase, achieves a significant determination of alfuzosin (ALF) enantiomers along with solifenacin (SOL) simultaneously. Enantioseparation of ALF was firstly evaluated in the reversed-phase mode using five polysaccharide-based Lux columns (Amylose 2 and Cellulose 1–4), highlighting Lux Cellulose 2 to reach the best enantioselectivity. Central composite design with Derringer's desirability function was then adopted to optimize the chromatographic conditions for an acceptable resolution. A mobile phase composed of ethanol and phosphate buffer, pH 4, (30:70, v/v) at a rate of 0.5 mL/min with UV-detection at 215 nm, exhibits good separation of ALF-enantiomers from SOL with resolution values of 1.45 and 2.64, respectively. The method’s greenness profile has been assessed and compared with that of mostly reported ones via the newest comprehensive analytical method greenness score (AMGS) calculator. The proposed method is considered a straightforward approach towards safer, more economic, eco-friendly and comparatively favorable for the cited drugs’ quantification in their formulation.

Tantawy, M. A., H. A. El Fiky, A. M. Badawey, M. F. Abd El Ghany, and N. V. Fares, "A Novel Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotubes for Potentiometric Xipamide Determination", Journal of The Electrochemical Society, vol. 168, issue 5: The Electrochemical Society, pp. 056506, 2021. AbstractWebsite

Solid contact electrodes are widely used in analytical fields due to their outstanding performance over classical ones. However, they showed formation of a water layer affecting stability of those electrodes’ type. Herein, we develop a solid contact ion selective electrode to overcome this common drawback through application of multi-walled carbon nanotubes as a hydrophobic layer between the ion sensing membrane and a glassy carbon electrode. This fine modification improved stability of the electrode via preventing the formation of this water layer. The obtained potential was steady over 30 days with a drift of ∼0.8 mV h−1. The MWCNTs-modified electrode was used for determination of xipamide with a Nernstian slope of −56.01 over a linearity range of 1.0 × 10−5–1.0 × 10−2 mol l−1 and detection limit of 6.0 × 10−6 mol l−1. The proposed sensor was effectively applied for determination of the cited drug in its marketed pharmaceutical dosage form and spiked human plasma.

Kelani, K. M., M. A. Hegazy, A. M. Hassan, and M. A. Tantawy, "Determination of naphazoline HCl, pheniramine maleate and their official impurities in eye drops and biological fluid rabbit aqueous humor by a validated LC-DAD method", RSC Advances, vol. 11, issue 12: The Royal Society of Chemistry, pp. 7051 - 7058, 2021. AbstractWebsite

A simple RP-HPLC-DAD method was developed and validated, as per the ICH guidelines, for simultaneous determination of naphazoline HCl (NPZ) & pheniramine maleate (PHN) along with three of their official impurities. Chromatographic separation was performed on a hypersil ODS column (5 mm, 250–4.6 mm i.d.) with isocratic elution using phosphate buffer pH 6.0: acetonitrile (70 : 30, v/v) as mobile phase, at a flow rate of 1.0 mL min−1 and UV detection at 260.0 nm. The developed method was found to be linear over the concentration ranges of 5.00–45.00 μg mL−1 for NPZ and NPZ impurity B and 10.00–110.00 μg mL−1, 10–70 μg mL−1 and 10–120 μg mL−1 for PHN, and PHN impurity A and B, respectively, with correlation coefficient values <0.999 for the five cited compounds. The method was confirmed to be accurate, robust and precise with RSD >2.0%. LOD and LOQ values for the five cited compounds were calculated. Moreover, the method was also validated in rabbit aqueous humor as per the US food and drug administration (FDA) bioanalytical validation guidelines. Finally, the proposed method was applied for the analysis of the two drugs along with their impurities in dosage form and spiked aqueous humor samples.

Abdel-Moety, E. M., M. R. Rezk, M. Wadie, and M. A. Tantawy, A combined approach of green chemistry and Quality-by-Design for sustainable and robust analysis of two newly introduced pharmaceutical formulations treating benign prostate hyperplasia, , vol. 160, pp. 105711, 2021. AbstractWebsite

This work represents a combined approach of green chemistry and analytical Quality-by-Design principles for developing sustainable HPLC-DAD methods with high operational flexibility and reliability. Two newly introduced pharmaceutical combinations were analyzed; the first one (mixture I) composed of tamsulosin and tadalafil, while the second (mixture II) was a mixture of alfuzosin and solifenacin. To achieve this goal, monolithic-based C18 column was utilized for its characteristic rapid flow and short analysis time in addition to expressing low back-pressure upon using ethanol as a green organic solvent. Analytical Quality-by-Design approach was conducted by applying quality risk assessment and scouting analysis followed by screening five chromatographic parameters via Placket-Burman design. Critical method parameters were thoroughly identified and then optimized using central composite design and Derringer’s desirability function. The optimized mobile phase was composed of ethanol and phosphate buffer (pH 4.0) in a ratio of 40:60 (v/v) for mixture I and in a ratio of 50:50 (v/v) for mixture II. The flow rate was adjusted at 2.3 mL/min with UV detection at 210 nm for both mixtures. Design space was then assigned to estimate the operating regions that guarantee satisfactory results and robust analysis. The proposed methods were validated as per ICH guidelines with peak purity assessment and careful robustness monitoring around the created design space. Moreover, the methods showed good applicability for determination of the cited drugs in their marketed formulations and evaluating their content uniformity. Finally, environmental impact of the methods was comparatively appraised by three state-of-the-art metrics, namely; National Environmental Methods Index, Analytical Eco-Scale and Green Analytical Procedure Index.