fruits rind by using high-performance thin-layer chromatography. Asian Journal of Chemistry 23(2), 788-790 (2011). A simple HPTLC method has been developed for estimation of beta-carotene in fruit rind of Diplocyclos palmatus (Cucurbitaceae). The rind of fruits was extract with acetone. HPTLC on silica gel with petroleum ether as mobile phase. The hRf value of beta-carotene was 30. Densitometric evaluation at 450 nm. The method was linear in the range of 6-60 ng/band. The recovery was 99.4 % for beta-carotene.

J. Planar Chromatogr. 23, 282-285 (2010). HPTLC of compactin and citrinin on silica gel with toluene - ethyl acetate - formic acid 3:2:1 in a twin-trough chamber saturated for 30 min at room temperature and a relative humidity of 60 +/- 5 %. Quantitative determination by absorbance measurement at 238 nm and 366 nm. The hRf of compactin and citrinin was 47 and 62, respectively. Good correlation was obtained between peak area and concentration, with a determination coefficient r2= 0.998 for compactin and 0.996 for citrinin.

J. Planar Chromatogr. 23, 286-288 (2010). TLC of taxol with a stationary-phase gradient whereby parts of different TLC plates were connected by use of a MIGAS device. Separated taxol-containing zones were developed with methanol over 1 cm and thus moved to another plate. The lipophilic substance zone was cut out after separation of the sample on a silica gel plate with n-heptane - ethyl acetate 1:1. Further separation of taxol from accompanying hydrophilic substances was carried out on HPTLC RP-18W with methanol - water 4:1. The taxol-containing fraction was finally separated on silica gel with chloroform - acetone 3:1 in a horizontal chamber at constant temperature (30 +/- 1°C) and humidity (35 +/- 1 %). Detection under UV 254 and 366 nm. Quantitative determination by densitometry at 220 nm. The precision (n = 7) was 0.63 % and the repeatability (n = 7) 3.35 %. The limit of detection and quantification was 0.50 and 1.00 µg/zone, respectively; the correlation coefficient from linear regression was >0.98, and the linear calibration range was 1 - 10 µg/zone.

J. Planar Chromatogr. 23, 339-342 (2010). HPTLC of saccharin in foodstuffs (e. g. cola drinks, lemon juices, betel nut powder, mouth fresheners, ice candy, and tabletop sweeteners) on silica gel with chloroform - methanol - acetic acid 64:35:1 or acetone - isopropanol - acetic acid 60:39:1. Quantitative determination by absorbance measurement at 230 nm. Linearity was between 250 - 1250 ng/µL. The limit of detection and quantification for saccharin were 40 and 130 ng, respectively. Mean recovery from spiked samples was 102.3 % for cola drinks and 98.8 % for lemon juices. Relative standard deviation (% RSD) for cola drinks, lemon juices, ice candy, mouth freshener, betel nut powders, and tabletop sweeteners were 2.1, 4.2, 3.4, 3.0, 4.9, and 4.1 %, respectively.

J. Chromatogr. A 1218 (19), 2692-2699 (2011). HPTLC coupled with bioluminescence detection can be used for screening for unknown substances. So far the HPTLC plate was dipped in an aqueous solution of Vibrio fischeri bacteria. However polar substances may be dissolved during this process, which leads to blurring and tailing of the zones on the plate. This was overcome by application of the bacteria solution by rolling. A rolling device was made of commercially available household articles and tested using octhilinone and methylparaben. Comparison of rolling with dipping showed that despite the manual steps involved in the rolling process, the results were reproducible. Depending on the substance and its amount on the HPTLC plate, with rolling peaks were narrower, up to a factor of 4 higher and showed a higher signal-to-noise ratio than with dipping.

62nd Indian Pharmaceutical Congress Abstract No. F-13 (2010). HPTLC of risperidone in bulk and pharmaceutical dosage form on silica gel with dichloromethane – methanol – ethanol – triethylamine 120:120:60:1. Quantitative determination by absorbance measurement at 280 nm. The linearity was obtained in the range 4-8 µg/spot (r2 =0.9989). The limit of detection and the limit of quantification for risperidone were 98 ng/zone and 599 ng/zone, respectively. The recovery was 99.5 %.

Acta Chromatographica 22 (2), 297-305 (2010). Description of a simple, precise, and accurate method for simultaneous quantification of aspirin, atorvastatin calcium and clopidogrel bisulphate by HPTLC on silica gel with toluene – methanol - formic acid 65:35:1. The hRf values were 26, 47, and 78 for aspirin, atorvastatin calcium, and clopidogrel bisulphate, respectively. Quantification by densitometry at 254 nm. The precision intra-day and inter-day was in the ranges of 0.2–0.7 %RSD and 0.5–1.0 %RSD for aspirin, 0.4–0.9 %RSD and 0.4–0.6 %RSD for atorvastatin calcium, and 0.3–0.7 %RSD and 0.4–0.9 %RSD for clopidogrel bisulphate.

J. AOAC Int. 93, 754-764 (2010). The review describes analytical methods for drug substances, formulations, and clinical samples analyzed and validated by HPTLC during the period 1996-2009. Procedures, materials, and instrumentation for the different steps in the chromatographic procedure and validation of results are given; application to bulk drugs, formulations, stability studies, biological samples (e.g., urine and plasma), and hydrophobicity studies; and prospects for the future use of HPTLC for drug analysis are described. The sections cover the experimental procedures (sample preparation, stationary phases, mobile phases, application of standards and samples, chromatogram development, detection, documentation of chromatograms, densitometric quantitative analysis), determination of hydrophobicity, confirmation of zone identity, method validation, chiral separations, micropreparative layer chromatography, applications of HPTLC-densitometry, and future prospects for HPTLC in drug analysis. 155 references are reviewed.