Acta Chromatographica 22 (2), 259-265 (2010), DOI:10.1556/AChrom.22.2010.2.8. Description of a new, simple, precise, and accurate method for quantification of (-)-epicatechin in the leaves of Cassia fistula by HPTLC on silica gel with toluene – ethyl acetate – formic acid – methanol 205:3:1:1. Quantification by densitometry at 280 nm. The linearity was in the range of 200–800 ng/band. Method precision was 1.4 %RSD and instrumental precision 1.1 %RSD. Recovery was 98.1 % and specificity regarding matrix was given.

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. AOAC Int. 93, 804-810 (2010). HPTLC of rutin on amino phase with ethyl acetate - formic acid - methanol - water 100:9:11:17 at room temperature. Detection by spraying with natural products reagent. Linearity was between 0.95 and 4.78 µg/zone. LOD and LOQ were 330 and 630 ng/zone, respectively. The %RSD for six replicates at three concentration levels was less than 3 %, while the recovery was between 97.3-103.3 %. For the three-dimensional image analysis of chromatograms images were taken from each plate using a HP flatbed scanner at an optical resolution of 300 dpi in normal mode. The pictures were stored in TIFF file format. Evaluation was performed using Melanie 7.0 software. Following automatic detection of the zones the program computed the 3D image of a selected region from the HPTLC plate. The volume of the resulting cone-shaped zone was used as numerical data to construct the calibration curve.

J. Planar Chromatogr. 24, 487-490 (2011). HPTLC of vitamin D3 in fish oil after saponification and purification on silica gel with chloroform - diethyl ether 9:1 with chamber saturation for 20 min. Quantitative determination at 280 nm. Linearity was between 200 and 1000 ng/band. The LOD and LOQ were 29 and 232 ng/band, respectively. The repeatability (RSD) was 4.6 %; the %RSD for intermediate precision was 0.9; the %RSD for intra-day precision (n = 6) was between 2.9-5.9 % and the %RSD for inter-day precision (n = 6) was between 3.2-6.4 %. Recovery was 97.6 - 104.2 % with a %RSD of 3.9 - 4.8 %.

J. Liq. Chromatogr. Relat. Technol. 34, 1850-1869 (2011). HPTLC of pipazethate (1) and its degradant 10H-pyrido[3,2-b][1,4] benzothiadiazine-10-carboxylic acid (2) on silica gel with chloroform - diethylamine - methanol 94:1:5. Quantitative determination by absorbance measurement at 225 nm. The hRf values of (1) and (2) were 35 and 28, respectively. Linearity was between 2-9 µg/zone for (1) and 1-6 µg/zone for (2). Limits of detection and quantification were found to be 53 and 180 ng/zone for (1), and 40 and 130 ng/zone for (2), respectively. Recoveries (by standard addition) were 100.1 % for (1) and 99.5 % for (2). Comparable results were obained with a validated HPLC method.

J. Liq. Chromatogr. Relat. Technol. 34, 2548-2464 (2011). HPTLC of tocopherol acetate (1) and tocopherol (2) in oral fluid vitamin E on silica gel with chloroform - cyclohexane 11:9. Quantitative determination by absorbance measurement at 202 nm for (1) and 272 nm for (2). The hRf values of (1) and (2) were 47 and 38, respectively. Linearity was in the range of 2-8 µg/band for (1) and (2). Limits of detection and quantification were found to be 50 and 150 ng/zone for (1). Precision was below 2 %. The intermediate/inter-day/intra-day precision was 0.4 % (n = 6). Recovery (by standard addition) was in the range between 99.8-101.5 %. Tocopherol acetate was better separated from tocopherol using normal phase TLC than by reversed phase TLC.

J. AOAC Int. 94, 1422-1426 (2011). HPTLC of eleutherosides B, E, and E1 in the fruits and leaves of E. senticosus and five other species of Eleutherococcus species after extraction with SPE, on silica gel in the horizontal chamber with saturation for 20 min, with a two-step development with 1) chloroform - methanol - water 70:30:4 and 2) chloroform - methanol - toluene - ammonium hydroxide 9:6:3:2. Detection by immersion in Liebermann-Burchard reagent for 1 s and heating at 110 °C for 10 min. The hRf values for the eleutherosides E, B, and E1 were 43, 53, and 66, respectively.

Indian Drugs 48(4), 49-55 (2011). HPTLC of hydrochlorothiazide (HCZ), amlodipine besylate (AMB) and valsartan (VAL) on silica gel with ethyl acetate - methanol - 10 % ammonia 17:4:2. The hRf value was 26 for AMB, 34 for VAL and 82 for HCZ. The linearity range was 100-700 ng/band for VAL and HCZ and 50-400 ng/band for AMB.