J. Food Compos. Anal. 77, 39-43 (2019). TLC of marine oil omega-3 supplements on silica gel with hexane - diethyl ether - glacial acetic acid 50:10:1. Detection by spraying with anisaldehyde solution, following by heating using a heat gun. Analysis of samples allowed the identification of different sources of omega-3 polyunsaturated fatty acids (PUFA) in their natural triacylglycerol (TAG) or concentrated ethyl ester (EE) forms.

J. Food Compos. Anal. 80, 16-32 (2019). Review of methods and techniques for the analysis of adulterants in honey, including TLC and HPTLC. Originally TLC was used to detect honey adulterated with high fructose corn syrup. HPTLC has been used for the detection of sucrose, fructose or glucose in commercial honeys.
 

J. AOAC Int. 102, 776-780 (2019). HPTLC of sibutramine, phenolphthalein, and three PDE5 inhibitors (sildenafil, vardenafil and tadalafil), as well as caffeine, fluoxetine, theophylline, and acetaminophen as adulterants in weight loss products on silica gel with methyl tert-butyl ether – toluene – methanol 8:2:1. Densitometric absorption measurement at 225 nm. The hR_F values of reference substances increased in the following order: fluoxetine, sildenafil, vardenafil, caffeine, theophylline, tadalafil, acetaminophen, phenolphthalein and sibutramine. The method was successfully used for the screening of 12 commercial products. Of those, nine products tested positive for at least one undeclared component.

J. AOAC Int. 102, 720-725 (2019). HPTLC fingerprint of 98 batches of four commonly used traditional Chinese medicines dried tangerine peel (Chen Pi), green tangerine peel (Qing Pi), immature bitter orange fruit, and bitter orange fruit (Zhi Qiao) from two similar Citrus spp on silica gel with chloroform - methanol - water - acetic acid 26:8:2:3. Detection by spraying with 5 % aluminum chloride in ethanol, followed by examination under UV light at 366 nm. Artificial neural network analysis was applied to raw HPTLC fingerprints without any image processing and by manual image processing followed by chemometrics modeling (k-nearest neighbors and partial least-square discriminant analysis).

J. Liq. Chromatogr. Relat. Technol. 42, 324-329 (2019). HPTLC of individual pharmaceutical products containing moxifloxacin HCl (1), ofloxacin (2), amoxicillin trihydrate (3), acetylsalicylic acid + acetaminophen + caffeine (4), nimesulide (5), irbesartan (6), and pantoprazole (7) on silica gel with methanol - ammonium hydroxide - water 7:2:1 for (1), methanol - ethyl acetate - ammonium hydroxide 7:7:3 for (2), acetone - water - methanol - glacial acetic acid 20:10:5:2 for (3), ethyl acetate - glacial acetic acid 19:1 for (4), toluene - acetone 10:1 for (5), ethyl acetate - acetone - glacial acetic acid 180:40:1 for (6) and ethyl acetate - methanol - toluene 4:1:2 for (7). Quantitative determination by absorbance measurement at 366 nm. The hRF values for (1) to (3) and (5) to (7) were 72, 30, 80, 33, 40 and 43, respectively. The hRF values for (4) were 62 for acetylsalicylic acid, 49 for acetaminophen and 22 for caffeine. The quantitative methods were used to transfer the Global Pharma Health Fund (GPHF) Minilab Manual and U.S. Food and Drug Administration (FDA) Compendium to HPTLC following a model process for moxfloxacin HCl, ofloxacin, and amoxicillin trihydrate. The results met the guidelines of the model process regarding the calibration curves: r-values were at least 0.99, assays were within 85–115% specification limits of the label values of individual tablets and capsules, validation recoveries were within 95 - 105 % at all three spike levels, RSDs were no higher than 3 % for assays and validation analyses, and peak identity and peak purity checks had correlation factors of at least
0.99. 
 

J. Liq. Chromatogr. Relat. Technol. 42, 238-248 (2019). Review of recent applications of TLC in medicinal chemistry, including the determination of lipophilicity of biologically active compounds and its influence as activity descriptors of absorption, distribution, metabolism, elimination and toxicity. Practical applications of TLC as a fast screening technique in different stages of monitoring processes were also described, including systems recently used for stability studies of selected drugs.

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, 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 %.