J Pharm Bioallied Sci. 12(2), 139-145 (2020). An HPTLC method was validated for the fingerprint of flavonoids and other phenolic compounds (rutin, apigenin, luteolin, caffeic acid, chlorogenic acid, rosmarinic acid) in methanol macerates of dried aerial parts of five Lamiaceae (subfamily Nepetoideae: Dracocephalum moldavica, Lophanthus anisatus, Monarda fistulosa, Ocimum americanum, Satureja hortensis). HPTLC of extracts and standards on silica gel with chloroform – ethyl acetate – formic acid 5:4:1 or with ethyl acetate – formic acid – water 15:1:1. Detection under UV light before and after spraying with aluminium chloride 1 % in methanol. Rosmarinic acid was present and abundant in all extracts and was also quantified by densitometry at UV 366 nm without derivatization. The LOD was 29.2 µg/mL; the rosmarinic acid concentration range was between 12.6 mg/g (Lophanthus) and 24.8 mg/g (Dracocephalum).

J. of Chromatogr. Sci. 59 (6), 576-583 (2021). HPTLC of simeprevir (SMV) and sofosbuvir (SOF) on silica gel with ethyl acetate – hexane - methanol 5:4:1. The hRF of SMV was 67 and of SOF 43. Quantitative determination by densitometry at 273 nm. The linearity range was between 60-1000 ng/band for SMV and 70-1200 ng/band for SOF, with good correlation coefficients (0.9993-0.9997) for both.  LOD was 15 and 22 ng/band and LOQ 44 and 66 ng/ band for SMV and SOF, respectively.

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. 59 (2), 140-147 (2021). TLC of paracetamol (PC), propyphenazone (PZ) and caffeine (CF) in the presence of the two PC impurities 4-aminophenol and 4-nitrophenol, on silica gel with chloroform - toluene - ethyl acetate - methanol - acetic acid 60:60:10:20:1. Quantitative determination by densitometry at 220 nm.

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), 418 - 426 (2020). Development of a method for the quantitation of glibenclamide (GLIBEN), rosiglitazone maleate (ROSI) and metformin hydrochloride (MET) from a combined dosage form by HPTLC on RP-18 F254s aluminum layer with methanol - tetrahydrofuran - water - glacial acetic acid 40:9:10:1. Detection under UV light. The hRf for GLIBEN, ROSI and MET was 54, 62 and 80, respectively. Quantification and photodocumentation by densitometry. For GLIBEN and  ROSI the LOD and LOQ was 80 and 200 ng/zone, for MET the LOD and LOQ was 48 and 120 ng/zone, respectively. The linearity for GLIBEN and ROSI was 200 - 1000 ng/zone (r = 0.9991 for GLIBEN and r = 0.9993 for ROSI) and for MET 120 - 600 ng/zone (r = 0.9988). The method was precise and accurate for all three drugs, and well suitable for the analysis of triglucored tablets, and reliable quality control for GLIBEN, ROSI and MET in a combined dosage form.

J. of Chromatogr. Sci. 58 (5), 411 - 417 (2020). Analysis of a binary mixture of silymarin (SR) and vitamin E (VE) acetate in their pure forms, pharmaceutical formulation and spiked human plasma, by HPTLC on silica gel with hexane - acetone - formic acid 140:60:3, detection at UV 215 nm, and quantification by densitometry. The linearity was 0.2 - 2.5 and 0.2 - 4.5 μg/band for SR and VE, respectively. Accuracy was 99.9 ± 1.2 % and 100.2 ± 1.6 % for SR and VE, respectively. The method was successfullly used for the determination of the studied drugs in their pharmaceutical formulation without any interference from excipients, and in spiked plasma samples. Statistical comparison of the results obtained by this HPTLC method showed no significant difference to the results obtained by the reported HPLC method.