Anal. Bioanal. Chem. 411, 725-734 (2019). HPTLC of bisphenol A (1) and its nine brominated analogs, namely monobromobisphenol A (2), 2,2’-dibromobisphenol A (3), tribromobisphenol A (4), tetrabromobisphenol A (TBBPA) (5), TBBPA mono(methyl ether) (6), TBBPA mono(allyl ether) (7), TBBPA mono(2,3-dibromopropylether) (8), TBBPA bis(allyl ether) (9), TBBPA bis(2,3-dibromopropyl ether) (10) in chicken samples on silica gel with n-hexane - ethyl acetate - dichloromethane - acetic acid 25:5:5:1. Detection at UV 254 nm. Further analysis by high-performance liquid chromatography-diode array detector/triple quadrupole mass spectrometry. The hRF values for (1) to (10) were 30, 32, 33, 45, 58, 68, 69, 69, 91 and 86, respectively.  

J. Liq. Chromatogr. Relat. Technol. 44, 87-94 (2021). HPTLC fingerprinting of Selinum
tenuifolium on silica gel with toluene - ethyl acetate - formic acid 13:11:2. Detection under UV light at 254 nm and 366 nm. The hRF values for gallic acid and ferulic acid were 36 and 58, respectively. 

Foods 9(8), 1136 (2020). TLC of methanolic decoctions and ultrasonication extracts from Zingiber officinale (Zingiberaceae) rhizomes, as well as from commercial ginger formulations, on reverse-phase C18-silica gel with ethanol – water 13:7. Densitometry at 200 nm in absorbance and reflectance modes for 6-shogaol (SHO, hRF 36) and 6-gingerol (GIN, hRF 53). Standards of these vanilloid phenolics were also used for calibration; linearity was in the range of 100–700 ng for SHO and of 50–600 ng/band for GIN; interday and intra-day precisions were below 1.6 %. The LOD and LOQ was 34 and 101 ng for SHO, 17 and 51 ng for GIN, respectively. Recovery rates were 98.8–101.6 % for SHO and 99.0–101.5 % for GIN. For each extract, SHO and GIN levels were calculated, the yields after ultrasonication extraction were 10-25 % higher than with the corresponding decoctions. Comparison with other published methods (LC-MS and HPLC) showed superiority of this new method in terms of linearity range, accuracy and precision.

J Am Soc Mass Spectrom 31(9), 1981-1993 (2020). Low-temperature plasma-mass spectrometry was studied for comparison between direct desorption (DD) and diode laser assisted desorption (LD) in terms of quantitative and qualitative analysis of compounds from cellulose vs. silica gel TLC layers. Compounds (the 20 common amino acids, propofol, nicotine, cotinine, salicylamide, acetylsalicylic acid, paracetamol, caffeine, valprolactone and its isomer 4-ene-valproic acid) were applied on the TLC plates (without development) at different concentrations; a commercial mixture of acetylsalicylic acid, paracetamol and caffeine was also applied on TLC plates, developed with dichloromethane – ethyl acetate 1:50, detection at UV 254 nm and quantitative MS. In general, DD provided good results on cellulose, where LODs where between 0.01 and 2.55 ng/mm2, whereas several compounds remained undetected on silica gel. LD however provided LODs on silica gel from 0.3 to 84 pg/mm2. Tandem MS with collision-induced dissociation was implemented to improve signals, LODs and to characterize the other analytical figures-of-merits (including detection of the main fragment ions, determination of optimal laser beam width and irradiance depending on the compounds). For the two metabolites of valproic acid, the ions and fragments had identical values; therefore, a mix of the two isomers had to be applied and separated with dichloromethane – methanol 50:1 before MS; one half of the plate was visualized for control by dipping into potassium permanganate reagent (7.5g KMnO4, 50g K2CO3, 0.75g NaOH in 1L water).

J. Planar Chromatogr. 33, 587-597 (2020). HPTLC of plumbagin in fresh roots of Plumbago zeylanica on silica gel with toluene - acetic acid 18:1. Quantitative determination by absorbance measurement at 272 nm. The hRF value for plumbagin was 44. Linearity was between 500 and 4000 ng/zone. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 1031 and 3439 ng/zone, respectively. Average recovery was 99.4 %.

Planta Medica 84(12-13), 902-912 (2018). A dichloromethane extract of Athrixia phyllicoides aerial parts (Asteraceae) was eluted on a silica gel column with different mixtures of ethyl acetate and hexane or methanol. This fractionation was monitored on TLC silica gel layers, using the combinations of the same solvents as mobile phases. Detection by derivatization with Natural Product Reagent and PEG, and visualization at UV 254 nm. This allowed the grouping of the fractions into 13 profiles and the isolation of three hydroxy-methoxyflavones and a coumarate.

J. Planar Chromatogr. 33, 481-487 (2020). HPTLC of resveratrol in the fruits of Morus alba on silica gel with hexane - ethyl acetate - glacial acetic acid 40:60:1. Quantitative determination by absorbance measurement at 302 nm. The hRF value for resveratrol was 56. Linearity was between 100 and 1600 ng/zone. Intermediate precision was below 2 % (n=6). The LOD and LOQ were 16 and 46 ng/zone, respectively. Recovery was between 90.3 and 96.5 %.

J. Planar Chromatogr. 33, 457-462 (2020). HPTLC of scopoletin (1) and gallic acid (2) in the aerial parts of Jatropha glandulifera on silica gel with toluene - ethyl acetate - glacial acetic acid 75:25:1. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) and (2) were 69 and 40, respectively. Linearity was between 100 and 600 ng for (1) and (2). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 70 and 200 ng for (1) and 40 and 100 ng for (2), respectively. Recovery was between 98.8 and 98.9 % for (1) and 97.4 and 98.1 % for (2).