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.

CBS 107, 13-15 (2011). HPTLC of 5-hydroxymethylfurfural (HMF) in honey on silica gel, prewashed with methanol - water 6:1, with ethyl acetate. Quantitative determination by densitometry in absorbance mode at 290 nm. Optional detection by immersion in p-aminobenzoic acid reagent followed by heating at 110 °C for 5-10 min. The hRf value of HMF was 80. The calibration function was polynomial in the range of 0.8-80 ng/band whilst Michaelis Menten 2 regression was suitable for higher concentrations. The LOD of HMF in honey samples was 0.75 mg/kg (12 µL applied) and the LOQ 2.4 mg/kg. The method complies with the requirement of max. 15 mg/kg of HMF in honey. The results with this method were compared with those obtained by the spectrophotometric Winkler method and by HPLC-UV and mean differences were minor (3.3 % or 0.9 mg/kg). Complementary confirmation by HPTLC-MS online coupling. HMF zones identified under UV were eluted and analyzed by ESI-MS in full-scan and SIM mode.

J. of Chromatogr. A 1218 (20), 3089-3084 (2011). Comparison of the separation of the structurally related angiotensin-converting enzyme (ACE) inhibitors lisinopril, cilazapril, ramipril and quinapril and their corresponding active diacid forms (prilates) by conventional TLC on silica gel with the separation on monolithic ultra-TLC (UTLC) phase. Technical modifications of the commercially available equipment for sample application, development and detection were necessary for the use with UTLC plates. Development in a modified horizontal developing chamber with ethyl acetate - acetone - acetic acid - water 16:4:1:2. Detection by absorbance measurement at 220 nm and after exposure to iodine vapors under daylight, as well as by image analysis. As a result the monolithic layer was more efficient for the separation of structurally similar polar compounds, such as prilates, than conventional silica layers. Confirmation of the identity of the compounds by ESI-MS after their online extraction from the UTLC and TLC plates.

Planta Med. 75, 1000 (2009). TLC and HPTLC of Mezereon (Daphne mezereum) bark extracts and scopoletin, umbelliferone, mezerein, and daphnetoxin on silica gel with various mobile phases containing toluene, ethyl acetate, and formic acid at different proportions. Detection under UV 254 and 366 nm and visible light. The applied procedure may be proposed for an updated and optimized TLC identification test of the homeopathic monograph of Daphne mezereum L.

Ham. Ex D. Don, Myricaceae. J. Planar Chromatogr. 23, 326-331 (2010). HPTLC of myrecitin and stem bark extracts on silica gel with toluene - ethyl acetate - formic acid - methanol 15:15:3:2. Quantitative determination by absorbance measurement at 268 nm. Linearity was between 0.4-2.0 µg/band. The limits of detection and quantitation were 93 ng and 284 ng/zone. The intra-day and inter-day precision of the method was in the range of 0.14-0.55 %. The recovery of myrecitin at three concentrations was in the range of 98.9-100.1 % and the average recovery was 99.3 %.