J. Planar Chromatogr. 29, 453-461 (2016). HPTLC of chlorzoxazone (1) and diclofenac potassium (2) in the presence of the nephrotoxic chlorzoxazone degradation product_x000D_
2-amino-4-chlorophenol (3) on silica gel with chloroform ‒ ethanol ‒ triethylamine 90:10:1. Quantitative determination by absorbance measurement at 230 nm. The hRF values for (1) to (3) were 63, 35 and 42, respectively. Linearities ranged between 1.5-5 μg/zone for (1), 0.5-4 μg/zone for (2) and 0.4-4 μg/zone for (3). The intermediate precisions were below 1.3 % (n=3). The LODs and LOQs were 320 and 980 ng/zone for (1), 140 and 450 ng/zone for (2) and 120 and 370 ng/zone for (3), respectively. Average recoveries were 100.2 % for (1), 99.3 % for (2) and 99.4 % for (3).

J. Ethnopharmacol. 198, 158-166 (2017). HPTLC of chlorogenic acid in the stems of Solanum xanthocarpum on silica gel with ethyl acetate – glacial acetic acid – formic acid – water 8:3:3:4. Quantitative determination by absorbance measurement at 254 nm. The hRF value for chlorogenic acid was 56.

J. Liq. Chromatogr. Relat. Technol. 40, 297-303 (2017). HPTLC of amygdalin on RP-18 with acetonitrile – water 1:1. Quantitative determination by absorbance measurement at 210 nm. The hRF value for amygdalin was 60. Linearity was between 2.5 and 50 μg/zone. LOD and LOQ were 1 and 4 μg/zone, respectively. The intermediate precision was <2 % (n=3). Recovery rate ranged from 99.9 to 100.6 %.

J. Chromatogr. Sci. 54 (4), 647-652 (2016). Presentation of a sensitive, accurate and selective method for the simultaneous determination of paracetamol (PAR), its toxic impurity 4-aminophenol (4-AP), pseudoephedrine HCl (PSH) and loratidine (LOR). HPTLC on silica gel with acetone – hexane – ammonia 40:50:1. Densitometric evaluation at 254 nm for PAR, 4-AP and LOR, and at 208 nm for PSH. The method was used for the determination of PAR, PSH and LOR in commercial tablets and in plasma in the ranges of 0.5–6.0 µg/zone, 1.6–12.0 µg/zone and 0.4–2.0 µg/zone for PAR, PSH and LOR, respectively. Comparison of the results obtained by the proposed method with those obtained by HPLC method showed no significance difference between both methods regarding accuracy and precision.

J. Planar Chromatogr. 30, 411-417 (2017). HPTLC of paraben solutions and a complex matrix such as honey spiked with 5-hydroxymethylfurfural to study the influence of different application parameters on quantitative analysis. The investigated parameters included application geometries (spot, band and area) and their respective application modes (contact and spray-on), various dosage speeds, different band lengths, overspotted application versus application of mixture solutions as well as influence of the dosing volume on the result. These parameters have influence on method development and validation results.

J. Planar Chromatogr. 30, 502-509 (2017). HPTLC of chlorogenic acid (1), gallic acid (2), caffeic acid (3), quercetin (4), p-coumaric acid (5) and kaempferol (6) in the fresh leaves, flowers, pods, and dried pods and seeds of M. oleifera on silica gel with toluene – ethyl acetate – formic acid 14:10:1. Quantitative determination by absorbance measurement at 282 nm. The hRF values for (1) to (6) were 1, 31, 41, 45, 49 and 52, respectively. Linearity was between 0.1 and 1.5 μg/zone for (1) to (6). LOD and LOQ were 142 and 382 ng/μL for (1), 126 and 343 ng/μL for (2), 114 and 410 ng/μL for (3), 116 and 301 ng/μL for (4), 125 and 356 ng/μL for (5) and 110 and 345 ng/μL for (6), respectively. The intermediate precision was <3 % (n=6). Average recovery was 96.2 % for (1), 97.9 % for (2), 97.3 % for (3), 96.5 % for (4), 97.1 % for (5) and 96.2 % for (6).

J. Chromatogr. A 1525, 173-280 (2017). Presentation of a straightforward, selective and sensitive screening method for the determination of 16-O-methylcafestol (16-OMC) in roasted coffee, the characteristic diterpene exclusively present in Coffea canephora which is an excellent marker for Coffea canephora admixtures to Coffea arabica. HPTLC with fluorescence detection (HPTLC–FLD), using sudan IV as internal standard and a direct saponification with 10 % ethanolic potassium hydroxide solution, followed by solid-supported liquid extraction with petroleum ether. Selective derivatization of 16-OMC with 2-naphthoyl chloride and analysis by HPTLC–FLD on silica gel with cyclohexane – t-butyl methyl ether – formic acid 43:7:1. Quantitative determination of the enhanced fluorescence at 244/>320 nm. The LOD and LOQ was 5 and 14 mg/kg of 16-OMC in coffee, which allowed for the determination of Coffea canephora admixtures to Coffea arabica below 1 %. The recovery for blends of Coffea arabica with Coffea canephora was close to 100 %._x000D_

J. Planar Chromatogr. 31, 230-234 (2018). HPTLC of hypoxoside in the roots of Hypoxis hemerocallidea on silica gel with chloroform – methanol – water 35:15:1. Quantitative determination by absorbance measurement at 257 nm. The hRf value for hypoxoside was 30. Linearity was in the range of 0.02-1.80 µg/mL. The LOD and LOQ for hypoxoside were 0.51 µg and 1.65 µg/mL. (Note by the editor: It can not be true that the start of calibration is below the LOD by a factor of 25.) The intermediate precision was below 5 %. Average recovery was 84 %.