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. 23, 359-364 (2010). TLC of four series of carbamates of 3-hydroxy- and 4-hydroxyphenyl-acetamides, 4-benzylpiperidine and 1-benzylpiperazine on RP-18 with mixtures of acetonitrile and water containing 45-90 % organic modifier, with chamber saturation for 2 h at ambient temperature. Detection under UV light at 254 nm. The results obtained were compared with theoretical lipophilicity calculated by use of ChemOffice, QikProp, and Pallas software.

Chinese J. Ethnomed. Ethnopharm. 1, 55-66 (2011). TLC of the extracts of Baibanting 1) for Gardenia jasminoides Ellis, on silica gel with ethyl acetate - acetone – methanol – water 5:5:1:1, detection under daylight and by spraying with 10 % sulfuric acid in ethanol and heating at 110 ºC; 2) for Cuscuta chinensis Lam, on polyamide phase with methanol - glacial acetic acid - water 4:1:5, detection by spraying with 3 % alumnium chloride in ethanol, evaluation under UV 366 nm; 3) for Malaytea scurfpea fruit, on silica gel with n-hexane - ethyl acetate 4:1, detection by spraying with 10 % KOH in methanol and evaluation under UV 366 nm. Quantification of gardenoside by HPLC. The procedures proved to be simple, accurate, reproducible, robust and suitable for the quality control of the medicine.

Planta Med. 76, 474-480 (2010). HPTLC of camptothecin and plant material extracts (roots, stems, leaves,and fruits) on silica gel with chloroform - ethyl acetate - methanol 9:10:1 in a twin trough chamber at 25 +/- 2°C and 40 % relative humidity. Quantitative determination by densitometry at 360 nm. Linearity was between 80 and 480 ng/zone with a correlation coefficient of 0.998 +/- 0.020. Instrumental precision (%RSD) was 0.5 %. Repeatability (%RSD) of sample and standard were 1.1 and 1.0 %. The LOD and LOQ were found to be 40 and 80 ng/zone, respectively. The accuracy of the method was proven by the average percentage recovery of 99.1 %.

J. Planar Chromatogr. 24, 257-263 (2011). HPTLC of hydrophilic and lipophilic constituents of Salvia miltiorrhiza and standards protocatechuic acid and aldehyde, salvianolic acid A and B, dihydrotanshinone I, rosmarinic acid, caffeic acid, cryptotanshinone, tanshinone II A, tanshinone I, and miltirone on silica gel with dichloromethane - ethyl acetate - formic acid 11:12:5 for the first development and petroleum ether - ethyl acetate - cyclohexane 15:11:14 for the second development with chamber saturation for 30 min. The first mobile phase separated the hydrophilic constituents salvianolic acid B, salvianolic acid A, rosmarinic acid, caffeic acid, protocatechuic acid, and protocatechuic aldehyde. Detection under UV light at 254 and 365 nm. After documentation the plates were placed in a second chamber and development with the low polarity mobile phase which separated dihydrotanshinone I, cryptotanshinone, tanshinone I and II A, and miltirone. Detection under UV light at 254 and 365 nm. Quantitative determination by densitometry in absorbance mode at 260 or 290 nm. The linear range was between 0.1-0.3 and 0.7-8.3 µg/zone. Instrumental precision was less than 4 % (n = 6). Precision on one plate was below 5 % (n = 6) and on different plates below 14 %. Depending on the substance, the limits of detection and quantification were between 14-22 and 69-276 ng/zone, respectively. The repeatability (n = 6) was between 1.3-3.4 %. Some of the compounds had similar hRf values: for rosmarinic acid 44, for salvianolic acid 43, for caffeic acid 49, for protocatechuic acid 49, for dihydrotanshinone 65 and for cryptotanshinone 63. Additional detection by spraying with 5 % sulfuric acid in ethanol.

International Journal of PharmaTech Research 3(2), 1179-1185 (2011). TLC of gatifloxacin on silica gel with toluene - acetic acid - triethylamine 8:5:1. The hRf value was 46. Quantitative determination at 288 nm. The method was found to be linear in the range of 200-400 ng/band with a mean recovery of 99.9 %. The drug was subjected to different stress conditions (acid, base, thermal, photolytic, oxidative) and the degradation products were well resolved from the main drug.