62nd Indian Pharmaceutical Congress Abstract No. F-332 (2010). TLC of ramipril and hydrochlorothiazide on silica gel with ethyl acetate – methanol – chloroform – glacial acetic acid 11:3:7:2. The hRf values were 28 and 49 for ramipril and hydrochlorothiazide,respectively. Quantitative determination by absorbance measurement at 210 nm. The method was linear in the range of 500-1900 ng/band for both compounds. The recovery was 98-102 % for both drugs. The results were comparable when the sample was analysed by a dual wave-length method. The proposed method can be used for analysis of formulation without any interference from excipients.

J. Liq. Chromatogr. Relat. Technol. 34, 902-919 (2011). HPTLC of seven sugars (D-glucose, D-galactose, D-mannose, beta-D-fructose, alpha-D-fructose, sucrose, maltose, lactose) in food samples on silica gel with n-butanol - isopropanol - acetic acid - boric acid solution (200 mg boric acid in 10 mL water) 6:14:1:3. Detection by dipping into either aniline diphenylamine o-phosphoric acid reagent or p-aminobenzoic acid reagent. Quantitative determination by absorbance measurement at 370 nm. The HPTLC method was more sensitive by a factor of 8 for detection of sugars when compared to HPLC; only fructose showed a slightly better LOQ (difference by factor of 3). LOQ was better than 63 ng for HPTLC and about 500 ng for HPLC. Method comparison showed a good correlation and only a mean difference between both methods of 1.5 % sugar content for many food samples analyzed. HPTLC is a fully compliant method for determination of sugars in food. Application in the bioanalytical field was shown as well.

J. Trad. Chinese Med. & Pharm. Consult. 3 (7), 368-369 (2011). Hormones have been widely applied in clinical practice, however, overdose hormones are liable to cause general anaphylaxis, and even serious harm to physical health. For quick identification of hormones in traditional Chinese preparations, TLC of the extracts of the preparations on silica gel with chloroform – petroleum ether (30-60 ºC) – methanol 5:3:1, detection at UV 254 nm. Identification of methyltestosterone, prednisolone acetate, estrone, ethinyloestradiol, prednisolone acetate, testosterone undecanoate, fluocinolone acetonide, dexamethasone, betamethasone sodium phosphate, and hydrocortisone acetate by fingerprint comparison with the standards. The method has been applied to the real life samples of four varieties of preparation. The results were compatible with those obtained by HPLC and MS-MS.

J. Chromatogr. A 1266, 168-174 (2012). RP-TLC plates modified with C18, C8 or C2 are available on the market, however, RP-plates with tunable polarity have not been reported. Because of the limited variety of RP-plates mobile phase optimization is needed which is often time consuming. The presented polarity-adjustable RP-UTLC plates simplify the mobile phase screening process and expand the selection of reversed phase plates. The plates were prepared using the glancing angle deposition (GLAD) technique to deposit SiO2 nanopillars on glass plates and functionalized with octadecyltrichlorosilane for hydrophobicity. By O2 plasma treatment the silane carbon chain was shortened and COOH groups were introduced to the surface, producing plates with finely tunable polarities. Confirmation of the tuning of surface polarities by measurement of retention behavior changes in the separation of a model dye mixture of Sudan blue and Sudan IV, the elution order of which reversed as a result of the change in surface polarity. Testing on commercial RP-plates showed no change in the separation behavior which proves that plasma treatment of GLAD structures with highly accessible surfaces improves control over interfacial properties, producing better reverse phase separations. UTLC of Sudan blue and Sudan IV in toluene on the new RP-UTLC plates in horizontal developing chamber with acetonitrile, detection in visual light by recording of the development process by video camera).

Chinese J. Econ. Forest Res. 31 (2), 142-145 (2013). Compared to other analytical techniques TLC has the advantage of no/minor sample pretreatment, simultaneous separation and determination of numerous and complex samples. Determination of polypeptide in protolysate of Camellia oleifera cake by TLC on silica gel with n-butanol – ethanol – water 4:1:1, detection by spraying with 0.5 % ninhydrin in propanone and heating at 105 °C for 15 min and viewing in daylight. Quantification of polypeptide by densitometry at 231 nm using glutathione (a tripeptide composed of glutamic acid, cysteine and glycine) as the external calibration standard. The %RSD for repeatability was 0.03 % (n=5). Recovery by standard addition was 106.9 % (%RSD=0.06 %, n=5). The LOQ was 2 µg/zone. The results of the TLC method for a batch of real life samples were comparable with the results by RP-HPLC.

J. Ethnopharmacol. 152, 292-301 (2014). HPTLC of extracts of Curcuma longa, Curcuma aromatica and Curcuma zanthorrhiza on silica gel with 1) toluene - acetic acid 4:1 (for curcuminoid determination), 2) acetonitrile - acetone - water 2:2:1 (sugars), and 3) dichloromethane (essential oils). Detection by dipping in anisaldehyde reagent (curcuminoid and essential oil systems) and aniline-diphenylamine-phosphoric acid (sugars) followed by heating at 100 °C, evaluation under white light and UV at 366 nm. Bis-demethoxycurcumin (hRF 18) was only present in Curcuma longa. The HPTLC results were compared with 1H-NMR spectroscopic analyses. The NMR analyses provided a sharper picture than HPTLC but only the combination of both methods enabled the authors of the study to understand both the general variability and the specific differences between the analyzed products.

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. 31, 389-395 (2018). HPTLC of paracetamol (1), pamabrom (2), and pyrilamine maleate (3) on silica gel with chloroform ‒ acetonitrile 3:7. Quantitative determination by absorbance measurement at 275 nm. The hRF values for (1) to (3) were 76, 46 and 12, respectively. Linearity ranged between 10-280 ng/zone for (1), 5-45 ng/zone for (2) and 1-20 ng/zone for (3). The intermediate precision was <2 % (n=3). The recovery was between 99.2 and 100.4 %.