J. Planar Chromatogr. 24, 274-280 (2011). Presentation of new reagents and visualization methods which enable the detection of particular substances. The best of them provide high selectivity and low detection limits and lead to a reliable analysis of the developed chromatogram. Three groups of chemical reactions are used for detection: oxidation, reduction, and complexation, as well as precipitation of colored precipitates. Oxidation and reduction are most widely used due to their selectivity, which allows detection and identification of the separated substances. Like this the target substance can be selectively visualized, as for example antioxidants in complex natural matrices. Innumerable chemical, physical, and biological methods of visualization are known. Required are new, more efficient reagents fo a selective visualization of a defined part of a substance or, in some cases, for a specific determination of a specific substance. The article describes the detection of food ingredients, medicines and pharmaceuticals, organic compounds not present in food, and inorganic compounds.

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.

European Journal of Medicinal Chemistry 45, 3719-3725 (2010). TLC of sulpiride and mebeverine hydrochloride on silica gel with absolute ethanol - methylene chloride - triethylamine 35:15:1. Quantitative determination by absorbance measurement at 221 nm. The method was linear in the range of 0.4-1.4 µg/band for sulpiride and 0.2-1.6 µg/band for mebeverine hydrochloride. The recovery was 100.4-101.0 %. The hRf value of sulpiride was 42 and of mebeverine hydrochloride 62. The results obtained by this TLC method were comparable with those by HPLC.

J. Planar Chromatogr. 24, 236-241 (2011). HPTLC of levodopa (LEV), carbidopa CAR), and entacapone (ENT) in a combined dosage form on RP-18 (prewashed with methanol) with acetonitrile - n-butanol - water - triethylamine 1:19:2:0.002, pH adjusted to 3.6 with phosphoric acid, in a twin-trough chamber saturated with mobile phase for 25 min. Quantitative determination by densitometry in absorbance mode at 282 nm. The hRf values were 46, 64, and 87 for LEV, CAR, and ENT, respectively. Linearity was between 300-1500 ng/zone for LEV, 200-1000 ng/zone for CAR, and 200-2000 ng/zone for ENT. The intra-day and inter-day precision was below 1.8 % RSD for all drugs. The recovery for LEV, CAR, and ENT (n = 3) was between 101.0 and 102.4 %.

J. Liq. Chromatogr. Relat. Technol. 32, 567-577 (2009). HPTLC of 6-gingerol (1), 8-gingerol (2), 10-gingerol (3), and 6-shogaol (4) in commercial gingers on Lichrosphere silica gel with toluene - ethyl acetate 3:1. Detection by spraying with anisaldehyde-sulfuric acid reagent, followed by heating at 120 ºC for 10 min. Quantitative determination by absorbance measurement at 577 nm. Linearity was between 96-480 ng for (1), 39-196 ng for (2), 49-242 ng for (3) and 50-256 ng for (4). Limits of detection and quantification were 26 and 77 ng/zone for (1), 16 and 47 ng/zone for (2), 17 and 50 ng/zone for (3) and 33 and 99 ng/zone for (4). %RSD of repeatability and intermediate precision were below 5 %. Recoveries were between 99.7 and 104 % for (1)-(4).

J. Planar Chromatogr. 24, 253-256 (2011). HPTLC of yohimbine on silica gel, prewashed with methanol, with toluene - ethyl acetate - diethyl amine 7:2:1 in a twin trough chamber saturated with mobile phase for 10 min at 25 +/- 2 °C. Quantitative determination by densitometry in absorbance mode at 285 nm. Linearity was between 400 and 1200 ng/band. The hRf value was 39. The repeatability as system precision and method precision (n = 6) was 0.9 and 0.8 % CV. The limit of detection and quantification was 80 ng and 260 ng. The instrument precision (n = 6), intra-day and inter-day precision (n = 3, %RSD) were 0.2, 0.1, and 0.1 %, respectively.

J. Liq. Chromatogr. Relat. Technol. 34, 864-887 (2011). Comparison of a one dimensional TLC-MS separation and fingerprinting method with a two-dimensional TLC-LC-MS method, when applied to the analysis of phenolic acids and flavonoids from Salvia lavandulifolia. TLC directly or indirectly coupled with mass spectrometric detection proved very useful in the analysis of the phenolic acid and flavonoid fraction selectively extracted from botanical material.

Research J. Pharm. and Tech. 3(1), 239-243 (2010). TLC of bumetanide in bulk drug and tablet formulation on silica gel with toluene - ethyl acetate - formic acid 14:7:1. The hRf value of bumetanide was 45 and it well resolved from degradation products. Quantitative evaluation by absorbance measurement at 335 nm. The method was linear in the range of 100-800 ng/band. The recovery was between 98.5-99.1 %. The sample was subjected to different stress conditions, e.g. acid, alkali, and photolytic oxidation.