Acta Chromatographica 21(2), 203-215 (2009). HPTLC of commercial products containing Heterotheca inuloides, Citrus aurantium, Peumus boldus, Equisetum arvense, Eucalyptus globulus, Ginkgo biloba, Mentha piperita, Aloe vera, Salvia officinalis , and Cassia senna on silica gel with different mobile phases. The mobile phase for aloin, boldine, chlorogenic acid, rutin, kaempferol, caffeic acid, and quercetin was ethyl acetate – methanol – water 100:17:13; for menthol, cineole, menthone, alpha- and beta-thujone, geraniol, linalyl acetate and linalool it was toluene – ethyl acetate 93:7; for ginkolide B toluene – ethyl acetate – acetone – methanol 50:25:25:3; and for sennoside B ethyl acetate – formic acid – acetic acid – water 100:11:11:27. Detection with natural products reagent, anisaldehyde reagent or Liebermann-Burchard reagent. We found that in only 20 % of the 40 commercial products analysed the chromatographic characteristics of the respective plants matched those of the specific respective marker compounds. This highlights a problem arising from the lack of regulation of these products, and emphasizes the need to develop simple and reliable analytical methods like TLC methods that can be performed in any laboratory for the purpose of quality control of dietary supplements or commercial herbal products sold in Mexico.

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.

CBS 105, 13-15 (2010). HPTLC of PVC foil samples on silica gel with isooctane – toluene – diethyl ether – ethyl acetate 8:7:4:1 after chamber saturation for 10 min, up to a migration distance of 65 mm. Detection of the biological activity of any compound migrated from the plastic foils in migration studies by dipping in Vibrio fischeri bacteria suspension and documentation with the Bioluminizer. Also direct extraction of additives from plastic foils by the TLC-MS Interface coupled to an Agilent LC-MS system and recording of the eluted additives in the positive ESI mode. Exact masses of unknowns were calculated with MassWorks software allowing their improved specification and thus their confirmation.

Phytochem. Anal. 22, 258-262 (2011). TLC of gomisin A (1), gomisin N (2) and schisandrin (3) in the fruits of Schisandrae chinensis on silica gel with toluene - ethyl acetate - formic acid 14:6:1. Quantitative determination by direct analysis in real time mass spectrometry (DART-MS). Linearity of (1) - (3) was between 0.5 and 5 nmole. The limits of detection and quantification were 60-200 pmole for (1), and 58-192 pmole for (2) and (3). Recovery (by standard addition) for (1) - (3) was between 104.0 and 120.2 %. TLC-DART-MS method provides faster and more specific quantification compared with the conventional densitometric and HPLC-UV methods.

J. Chem. Pharm Res. 2(5), 92-96 (2010). TLC of ofloxacin and cefixime on silica gel with methanol - ethyl acetate - 25 % ammonia 7:7:3. The hRf value of ofloxacin was 61 and of cefixime 78. The method was linear in the range of 50-500 ng/band. The recovery was in the range of 99.3-102.2 %. Quantitative determination by densitometry in absorbance mode at 295 nm.

J. AOAC Int. 94, 735-742 (2011). HPTLC and TLC of ofloxacin on silica gel with ethanol - conc. ammonia 4:1 in a horizontal chamber. Quantitative determination by fluorescence measurement at 313 nm. Simulated samples at a residue level of 1 mg/m² were prepared by spreading the calculated amount of ofloxacin solution on 1, 5, and 10 dm² stainless steel surfaces. The hRf of ofloxacin was 56. The mean recovery (n = 6) was 88.6-95.3 % with a CV of 3.8-4.9 %. The LOD was 0.6 ng/zone and the LOQ was 2 ng/zone, but it was shown that these can be lowered by immersion of the developed plate into a solution of liquid paraffin - n-hexane 1:2 to approximately 0.3 and 0.9 ng/zone. The repeatability (system precision) was 4.2 % for 2 ng, and 3.7 % for 20 ng. The recovery was between 88.6-95.3 %.

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.

J. Planar Chromatogr. 24, 57-59 (2011). HPTLC of piperine on silica gel with toluene - ethyl acetate - diethyl ether 6:3:1 in a saturated twin trough chamber. The hRf of piperine was 40. Quantitative determination by densitometry at 337 nm. Linearity was between 15 and 75 ng/zone. LOD and LOQ was 5 and 15 ng/zone, respectively. The recovery was 94.5 %. The instrumental precision, repeatability, intra-day and inter-day precision (%RSD, n = 6) was 0.6 %, 0.8 %, 0.9 and 0.8 %, respectively.