J. Liq. Chromatogr. Relat. Technol. 42, 249-257 (2019). Review of HPTLC methods published after 2000 for the analysis of vegetables, including bioactive compounds such as indoles, glycolipids, carotenoids and anthocyanins. TLC methods for the identification and quantification of pesticide residues such as iprodione, vinclozolin, cymoxanil, deltamethrin and parathion were reviewed. TLC coupled with other non-chromatographic techniques for the analysis of inorganic species, mycotoxins, glycoalkaloids and polyamides was described.  

J. Liq. Chromatogr. Relat. Technol. 42, 266-273 (2019). HPTLC of aqueous, fermented plant preparations from Chamomilla recutita L. (1), Allium cepa L. (2), Equisetum arvense L. (3) and Hamamelis virginiana L. (4) of different harvest years on silica gel with ethyl acetate - toluene - formic acid - water 16:4:3:2. The method was combined with effect-directed analysis (EDA) and high-resolution mass spectrometry (HRMS). For α-/β-glucosidase assays, the plate was sprayed with 2 mL substrate solution (60 mg 2-naphthyl-α-D-glucopyranoside or 2-naphthyl-β-D-glucopyranoside in 50 mL ethanol), then sprayed with 1 mL sodium acetate buffer and 2 mL enzyme solution (500 units α-glucosidase), followed by incubation at 37 ºC for 10 min. Analysis of multi-potent compounds was also performed using the 2,2-diphenyl-1-picrylhydrazyl reagent and Gram-positive Bacillus subtilis assays, followed by recording of elution head-based HPTLC-ESI-HRMS spectra. 

J. Liq. Chromatogr. Relat. Technol. 42, 311-316 (2019). HPTLC of equol in cattle manure with methyl t-butyl ether - cyclohexane 1:1. The plate was scanned with a Time of Flight – Direct Analysis in Real Time – Mass Spectrometry (TOF-DART-MS) system. The hRF value of equol was 71. The LOD and LOQ for equol were 2.4 µg/zone and 4.5 µg/zone, respectively. 

J. Liq. Chromatogr. Relat. Technol. 41, 15-16 (2019). HPTLC of thymine (1), uracil (2), adenine (3), cytosine (4), guanine (5) and guanosine (6) in Ganoderma lucidum and Cordyceps sinensis on silica gel with dichloromethane - methanol - formic acid 160:45:16. Quantitative determination by absorbance measurement at 254 nm. Identification of nucleobases in the samples was reconfirmed by hyphenated HPTLC-MS. The hRF values for (1) to (6) were 83, 73, 46, 32, 23 and 10, respectively. The intermediate precision was below 5 % (n=3). 

J. Liq. Chromatogr. Relat. Technol. 42, 274-281 (2019). HPTLC of caffeine in caffeine-containing botanicals and caffeinated products on silica gel with toluene - acetone - formic acid 9:9:2. Detection by dipping into NP reagent (1 g of diphenylborinic acid aminoethylester in 200 mL of ethyl acetate), followed by derivatization with anisaldehyde reagent, then heating at 100 ºC for 3 min. Quantitative determination by absorbance measurement at 273 nm. The hRF value of caffeine was 70. Linearity was between 30 and 120 ng/zone. The intra-day and inter-day precision was below 5 % (n=3). The LOD and LOQ were 10 and 30 ng/zone, respectively. Recovery rate was between 101 and 118 %.

J. Planar Chromatogr. 32, 273-283 (2019). HPTLC of trimetazidine dihydrochloride (1) and its potential impurities, namely, piperazinecarboxaldehyde (2), trimethoxybenzyl alcohol (3), and trimethoxybenzaldehyde (4) on RP-18 with acetonitrile - methanol - 0.1 % aqueous ortho-phosphoric acid (pH 6.2) 9:9:2. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) to (4) were 21, 35, 50 and 85, respectively. Linearity was between 0.05-10 µg/zone for (1), 0.05-1.1 µg/zone for (2), 0.05-1.2 µg/zone for (3) and 0.04-1.0 µg/zone for (4). The intermediate precision was below 2 % (n=9). The LOD and LOQ were 20 and 50 ng/zone for (1) to (3) and 15 and 40 ng/zone for (4), respectively. Recovery rate was 99.6 % for (1), 100.5 % for (2), 100.1 % for (3) and 99.4 % for (4).

J. Planar Chromatogr. 32, 317-321 (2019). HPTLC of 2-chloroaniline (1) at trace levels
in quetiapine fumarate (2) on silica gel with toluene and methanol 7:4. Quantitative determination by absorbance measurement at 235 nm. The hRF value of (1) was 85. Linearity was between 2.5-12.5 ng/zone for (1) and 400-2400 ng/zone for (2). The intermediate precision was below 2 % (n=3). The LOD and LOQ of (1) were 0.02 and 0.05 ng/zone for (1) [Editor´s note: This seems to be erroneous.] and 1.27 and 3.87 ng/zone for (2), respectively. Recovery rate ranged between 98 and 100 % for (1) and (2).

J. Planar Chromatogr. 32, 329-334 (2019). HPTLC of orlistat on silica gel with chloroform - methanol 49:1. Detection by spraying with anisaldehyde - sulfuric acid, followed by heating at 120 °C for 5 min. Quantitative determination by absorbance measurement at 600 nm. The hRF value of orlistat was 75. Linearity was between 600 and 4000 ng/zone. The intermediate precision was below 2 % (n=6). The LOD and LOQ for orlistat were 140 and 466 ng/zone, respectively. Recovery rate was between 97.7 and 104.5 %.