J. of Chromatogr. Sci. 59 (6), 536-547 (2021). HPTLC of pregabalin (PGB) and amitriptyline (AMT) as an active binary mixture in pure forms or in human biological fluids (plasma/urine)  on silica gel with ethanol - ethyl acetate - acetone - ammonia solution 160:40:20:1. Detection by spraying with 3 % ethanolic ninhydrin solution. Quantitative determination by densitometry at 220 nm for AMT and 550 nm for PGB peaks after derivatization. The linearity range was 0.2 - 2.5 μg/band for PGB and 0.1-2.0 μg/band for AMT.

J. of Chromatogr. Sci. 59(5), 425–431 (2021). HPTLC of bromhexine hydrochloride (BHX), impurity B (IMB) and impurity C (IMC) on silica gel with hexane - acetone - ammonia solution 450:25:4. Quantitative determination by densitometry at 240 nm. The linearity was in the range of 0.40-10.00, 0.20-2.00 and 0.20-2.00 μg/band for BHX, IMB and IMC, respectively. Comparison with an HPLC method showed no significant differences regarding accuracy and precision.

J. of Chromatogr. Sci. 58 (8), 737-746 (2020). Presentation of a method for determination of the antimicrobial capability of the metabolite coriloxin, derived from mycoendophytic Xylaria sp. NBRTSB-20, and purified by column chromatography with its purity assessed by HPLC, UPLC-ESI-QTOF-MS, FT-IR and NMR. Determination of the antimicrobial capability by TLC–bioautography with the agar overlay technique. Evaluation under visible light. The LOD of coriloxin antimicrobial activity was 10 μg for Escherichia coli and 20 μg for Staphylococcus aureus and Fusarium oxysporum. Inter- and intra-day precision was below 6.6 %. The recovery was between 91.2 to 108.7 % with RSD values of 0.9-2.3 %.

J. of Chromatogr. Sci. 58 (6), 520 – 534 (2020). HPTLC of 10-hydroxy-2-decenoic acid (10-HDA) in royal jelly products marketed in Egypt, on silica gel with chloroform - acetic acid 10:1. Quantitative determination by densitometry at 210 nm. First and second derivative treatment of the data and comparison between three statistical regression methods: parametric, nonparametric and weighted regression (WR). Derivative treatment of the data improved the sensitivity of the chromatographic signals. The WR method was advantageous over the use of the other two models and resulted in an enhancement of the accuracy and precision of the 10-HDA analysis. Recovery was 99.9 % with WR and 99.6 and 98.6 % with the other statistical methods. Further, the royal jelly standard was subjected to forced degradation studies including the effect of hydrolysis, oxidation, photolysis and dry heat.

J. of Chromatogr. Sci. 58 (5), 427 - 432 (2020). HPTLC of ulipristal acetate (UPA) in presence of its degradation products on silica gel with ethyl acetate - toluene - glacial acetic acid 40:70:3. UPA was subjected to acid and alkali hydrolysis, oxidation, photo and thermal degradation. The hRF of UPA was 38. Quantitative determination by densitometry. The linearity range was between 400-3600 ng/band. LOD was 72 ng/band and LOQ 220 ng/band. The recovery was 100.1-100.7 %. The method is accurate, precise, robust, and specific to measure UPA in presence of degradants.

Quim. Nova. 43, 878-883 (2020). HPTLC of caryophyllene (1) and the diterpenic acids copalic (2), hydroxy-copalic (3), acetoxycopalic (4), agathic (5), and hardwickiic (6) in oilresin of Copaifera on silica gel with hexane - ethyl acetate 7:3. Detection by spraying with ethanol in 10 % sulfuric acid, followed by heating for 5 min. Qualitative analysis at 366 nm. The hRF values for (1) to (6) were 80, 50, 8, 28, 16 and 40, respectively.

J. Sep. Sci. 43, 3885-3901 (2020). HPTLC of erianin and gigantol in the stems of Dendrobium hercoglossum on polyamide film with methyl benzene - ethyl formate - formic acid 6:3:1. Detection by spraying with 10 % ethanol solution of sulfuric acid, followed by heating at 105 ºC.

J. Sep. Sci. 43, 2981-2988 (2020). HPTLC of citicoline (1) and piracetam (2) in presence of their degradation products on silica gel with methanol - chloroform - ammonium chloride buffer 9:1:2. Quantitative determination by absorbance measurement at 230 nm. The hRF values for (1) and (2) were 15 and 85, respectively. Linearity was between 0.2 and 4 µg/zone for both (1) and (2). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 56 and 180 ng/zone for (1) and 53 and 170 ng/zone for (2), respectively. Average recovery was 100.9 % for (1) and 99.8 % for (2).