Phytochem. Anal. 22, 367-373 (2011). HPTLC of thymoquinone in the seeds of Nigella sativa on silica gel with toluene – cyclohexane 4:1. Quantitative determination by absorbance measurement at 254 nm. The hRf of thymoquinone was 28. The linearity range was 100-1400 ng/zone. The limit of detection and limit of quantification was 50 and 150 ng/spot, respectively. Inter- and intraday precisions were 1.6 and 2.4 % (n=6), respectively. Recovery (by standard addition) was 100.1 %. The method is reproducible and selective for the analysis of thymoquinone with added advantages of low cost of reagents, speed and minimal sample preparation, satisfactory precision and accuracy.

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. Planar Chromatogr. 24, 136-139 (2011). HPTLC of ethanolic extracts of plant material and betaine on silica gel, prewashed with methanol, with methanol - water 9:1 in a twin-trough chamber saturated for 30 min. Detection under UV light at 254 and 366 nm and by spraying with Dragendorff’s reagent or with sulfuric acid reagent followed by heating at 120 °C for 10 min (Dragendorff’s reagent) or at 110 °C until the intensity of the fluorescent zones reached a maximum (sulfuric acid). Quantitative determination by densitometry at 550 nm. The calibration range was between 4 and 30 µg/band. LOD and LOQ was 1 and 4 µg/band, respectively. The repeatability (n = 6) was 1.7 %. The recovery was between 99.1-101.9 %. The inter-day and intra-day precision (n = 3) was between 1.1- 2.2 % and 1.2-2.2 %, respectively.

J. AOAC Int. 93, 1836-1843 (2010). HPTLC of 1) lamivudine-zidovudine on silica gel with ethyl acetate - toluene - methanol 12:5:3, quantitative determination by absorbance measurement at 289 nm; of 2) metronidazole with ethyl acetate - ammonia 50:1, quantitative determination by absorbance measurement at 313 nm; of 3) neviparine with ethyl acetate - toluene 3:1, quantitative determination by absorbance measurement at 289 nm; and of 4) quinine with ethyl acetate - toluene - acetone 22:3:5, quantitative determination by absorbance measurement at 327 nm in a twin-trough chamber lined with wetted filter paper and saturated for 20 min. The average repeatability (within-laboratory) was 1.9 %, with 73 % less than 2 % and 97 % at 2.6 % or less. The average reproducibility (among-laboratory) was 2.7 %. Mean hRf values for lamivudine, metronidazole, neviparine, quinine, and zidovudine were 19, 28, 34, 33, 57.

Planta Med. 74, 352-353 (2008). HPTLC of tetraphyllin, turneradiffusin, beta-arbutin, terniflorin, echinaticin, turneradin and methanolic extracts of Turnera diffusa on silica gel with ethyl acetate - acetic acid - water 190:10:1. Quantitative determination by densitometric absorbance measurement at 254 nm.

CBS 107, 2-4 (2011). To ensure effective cleaning of the reaction vessels in pharmaceutical production wool swabs are used to swipe a defined area of the vessel. The wool swabs are extracted with chloroform and the extracts are applied as rectangles of 4x3 mm. HPTLC on silica gel with toluene - ethyl acetate 3:2 with chamber saturation for 10 minutes. Identification of substances by densitometric spectra recording between 200-350 nm followed by 3-level calibration. Detection by spraying or immersion in methanol - sulfuric acid 9:1 and heating for 5 min at 105 °C. Evaluation under visible light and UV 366 nm.

International Journal of PharmTech Research 3(2), 909-918 (2011). TLC of paracetamol, aceclofenac and rabeprazole on silica gel (prewashed with methanol) with ethyl acetate - methanol - glacial acetic acid 90:10:1 with chamber saturation for 20 min. The hRf value of paracetamol, aceclofenac and rabeprazole was 79, 63 and 39. Quantitative determination by densitometry in absorbance mode at 275 nm. The method was linear in the range of 100-500 ng/band for paracetamol, 20-100 ng/ band for aceclofenac, and 2-10 ng/band for rabeprazole. The recovery was between 99.2-101.0 %.

J. Planar Chromatogr. 24, 381-387 (2011). TLC of methanolic extracts (from cigarettes, niswar, tobacco leaves, beedi, and gutka) and nicotin on silica gel with petroleum ether - acetone - diethylamine 19:5:1 in a twin-trough chamber with saturation at 25 +/-3 °C and a relative humidity of 42 +/- 5 %. Quantitative determination by densitometry in absorbance mode at 262 nm. The hRf value of nicotine was 57. Linearity was in the range of 250-1500 ng/zone with r = 0.997. LOD and LOQ were 3 and 10 ng/zone, respectively. The recovery (n = 6) was 98.1- 100.1 %. The precision (%RSD) for repeatability, intra-day and inter-day analysis was below 3 % for three different tobacco samples.