J. Sep. Sci. 33, 3794-3799 (2010). HPTLC of caffeine (1), theobromine (2) and theophylline (3) in different types of tea on silica gel with chloroform - dichloromethane - isopropanol 4:2:1. Quantitative determination by absorbance measurement at 254 nm. The hRF of (1), (2) and (3) was 65, 45 and 56, respectively. Limits of detection and quantification were 22 and 45 ng for (1), 23 and 46 ng for (2) and 22 and 43 ng for (3), respectively. The intra-day and inter-day precisions had a %RSD lower than 2.55 % (n=6) for all substances. Recoveries (by standard addition) were between 95.1-101.5 % for all the three methylxanthine derivatives. The values of LOD and LOQ obtained are similar with those obtained by HPLC.

J. Chromatogr. B 878 (17-18), 1337-1345 (2010). Use of rabbit liver esterase, Bacillus subtilis esterase, and cutinase from Fusarium solani pisi for the detection of 21 organophosphorus and carbamate pesticides by HPTLC-enzyme inhibition assays (HPTLC-EI) on silica gel with n-hexane - ethyl acetate - dichloromethane 13:4:3. HPTLC-EI assay of three groups of organophosphate and carbamate insecticides with 1) n-hexane - ethyl acetate 63:37, 2) chloroform - ethyl acetate 9:1, 3) n-hexane - acetone - dichloromethane 15:2:3. Detection by treatment with Fast Blue Salt B and enzymatically coupling to alpha-naphthol released from the respective acetate used as substrate. Quantification by densitometry at 533 nm. Calculation of enzyme inhibition factors derived from HPTLC-EI using linear calibration curves. Comparison to published inhibition constants showed good correlation. The limits of detection ranged from a few pg/zone for organophosphates as strongest inhibitors to a few ng/zone for most carbamates and was around 60 ng/zone for chlorpyrifos and 14 ng/zone for parathion without oxidation. The CUT was able to detect insecticides of high and low inhibitory power in the range of ng to µg/zone. The HPTLC-EI with rabbit liver esterase was applied to the analysis of apple juice and drinking water samples spiked with paraoxon (0.001 mg/L), parathion (0.05 mg/L) and chlorpyrifos (0.5 mg/L). The mean recovery was 71-112 % with standard deviations of 2.0-18.3 %.

Rec. Nat. Prod. 3/4, 178-186 (2009). An HPTLC method has been reported for quantitative estimation of alpha-mangostin in fruit pericarp of Garcinia mangostana (Hypericaceae). HPTLC on silica gel with chloroform - methanol 9:1 in a saturated chamber (10 min). The plate was derivatized with anisaldehyde sulfuric acid reagent. Densitometric quantification at 382 nm. Alpha-mangostin was detected as a compact band with hRf value of 46. The method was linear in the range of 1-5 µg/band. The maximum yield of alpha-mangostin was obtained from the plant by hot extraction with methanol.

J. Chromatogr. A 1218 (19), 2722-2731 (2011). Review on the features of TLC in the different areas of pharmaceutical analysis, like in-process and intermediate control, illustrated by impurity testing of active ingredients and final products, as well as its application in pharmaceutical research and development. Based on examples reported in the last five years it is shown that TLC is still a very popular and frequently used analytical method in the pharmaceutical industry, although there is a tendency in current pharmacopoeias for favouring HPLC.

Quim. Nova. 34, 330-334 (2011). TLC of rosmarinic acid in preparations of Rosmarinus officinalis on silica gel with acetone – formic acid – methylene chloride 50:17:170. Detection under UV 366 nm. Quantitative determination by solid state differential pulse voltammetry (DPV). Linearity was between 0.694x10-3 to 0.526x10-3 mol/L. The limits of detection and quantification were 1.2x10-5 and 3.6x10-5 mol/L, respectively. The intermediate/interday/intraday precisions were 3.03 % and 2.2 %, respectively. Recovery (by standard addition) was 96.3 % for rosmarinic acid. The method presented high recovery levels compared to an HPLC method.

Der Pharma Chemica 2(3), 8-18 (2010). HPTLC of berberine on silica gel with methanol – acetic acid – water 8:1:1. The band corresponding to berberine showed an hRf value of 74. Quantitative determination by absorbance measurement at 350 nm. The method was linear in the range of 100-500 ng/band. Different samples analysed by the proposed method were found to contain 11.8-12.5 mg/g berberine. The recovery was between 98.0-100.3 %.

Abstracts, 42nd Middle Atlantic Regional Meeting of the American Chemical Society, College Park MD, USA, May 21-24 (2011). The four TLC methods for acetaminophen, acetylsalicylic acid, ibuprofen, and chlorpheniramine maleate contained in the Compendium of methods developed by A.S. Kenyon and T.P. Layloff at the US FDA for use in countries with limited resources were transferred to quantitative HPTLC. The used sample preparation methods provide suitable calibration curves covering the range of 70-130 % of the label value of the products. Quantitative determination by absorbance measurement at 254 nm.

J. Sep. Sci. 34, 2397-2404 (2011). HPTLC of 23 newly synthesized N-substituted 2-alkylidene-4-oxothiazolidines on RP-18 with 1) methanol - water, 2) acetonitrile - water, and 3) tetrahydrofurane - water. A quantitative structure-retention relationship study allowed to understand the chromatographic behavior of similar compounds.