Acta Chromatographica 20(4), 685-695 (2008). Determination of p-coumaric and protocatechuic acids in an ether fraction from a methanolic extract of Aquilegia vulgaris L. by HPTLC on silica gel with mixtures of heptane, dichloromethane, diisopropyl ether, formic acid, and water in various ratios. Satisfactory separation of the phenolic acids was achieved by use of the multiple gradient development technique. HPTLC results of the quantities of p-coumaric and protocatechuic acids were somewhat higher (0.396 and 2.584 mg/g dry plant material, respectively), than those determined by HPLC (0.374 and 2.283 mg/g dry plant material, respectively). Both methods were satisfactory in the precision, expressed as relative standard deviation, and are useful for quality control of Aquilegia vulgaris extracts.

Acta Chromatographica 20(4), 673-683 (2008). Presentation of a quantitative method for the analysis of lycopene in nutritional supplements consumed to reduce the risk of prostate cancer and other forms of cancer and cardiovascular disease. HPTLC on silica gel with petroleum ether – dichloromethane 9:1. Quantification by densitometry at 416 nm. Four products containing 300 µg, 3 mg, 5 mg, or 10 mg lycopene plus other ingredients were quantified using a lycopene standard: the measured amounts ranged from 77.7 to 98.1 % of the stated label values. The accuracy by spiked blank analysis was within 1.90 % of theoretical values for the 3 mg softgels and 1.10 % of theoretical values for the 10 mg softgels. The precision of replicate analyses showed a RSD of 1.44 % for the 10 mg softgels and 2.39 % RSD for the spiked blank for the 3 mg softgels. The results obtained for Lycopene standards available from two other companies showed 55.6, 57.6, and 20.0 % of the minimum amount expected from the stated label values.

Acta Chromatographica 21(3), 443-452 (2009). HPTLC on silica gel with ethyl acetate – hexane 3:17. Detection and quantification by densitometry at the maximum absorbance wavelength of 250 nm. The linearity was in the range of 60–260 ng/zone with r=0.9997. The limits of detection and quantification were 20 and 60 ng/zone, respectively. The precision and repeatability of the method were found to be 0.8 and 1.1 %, respectively. Recovery ranged from 97.9-100.1 %. The maximum zerumbone content in the rhizome was 1.81 %.

J. of Chromatogr. A 1218 (37), 6540-6547 (2011). New approach and application of highly automated planar chromatographic tools for powerful clean-up, called high-throughput planar solid phase extraction (HTpSPE), which is indispensable for preventing matrix effects in multi-residue analysis of pesticides in food by liquid and gas chromatography coupled to mass spectrometry, employing TLC to completely separate pesticides from matrix compounds and to focus them into a sharp zone, followed by extraction of the target zone by the TLC-MS interface, thus resulting in extracts nearly free of interference and free of matrix effects, as shown for seven chemically representative pesticides in four different matrices (apples, cucumbers, red grapes, tomatoes), and completion of clean-up of one sample in a manner of minutes. Regarding the clean-up step, quantification by LC–MS with mean recovery (against solvent standards) of 90–104% and relative standard deviations of 0.3–4.1% (n = 5) for two spiking levels of 0.1 and 0.5 mg/kg.

J. of Chromatogr. A 1218 (24), 3811-3815 (2011). HPTLC of sugars in bio-oil fractions on silica gel with acetonitrile - water 4:1, or mixtures of butanol and formic acid, followed by detection with the aniline - diphenylamine - o-phosphoric acid reagent. The method allowed for the separation of the anhydrosugars levoglucosan and cellobiosan, as well as glucose, arabinose, xylose and cellobiose without the need of pre-treatment and pre-derivatization of samples. Volatile compounds present in bio-oil did not interfere with sugar analysis, and the detrimental effect of the complex bio-oil matrix on columns and detector lifetime is avoided by using disposable HPTLC plates. It was found that the concentrations of levoglucosan and cellobiosan in bio-oil samples obtained from Pinus radiata sawdust were ranged between 1.3-2.3 % and 1.0-2.0 % respectively, while a higher levoglucosan concentration was in a bio-oil sample obtained from native wood.

J. Planar Chromatogr. 23, 373-375 (2010). HPTLC of carbosulfan on silica gel with n-hexane - acetone 4:1 in a saturated chamber. Detection by spraying with 10 % sodium hydroxide solution followed by potassium ferricyanide reagent. Semi-quantitative analysis after extraction is done against standards. Other carbamate, organophosphorus, organochlorine, and pyrethroid insecticides and constituents of viscera do not interfere. The detection limit of carbosulfan is ca. 500 ng.

J. Planar Chromatogr. 24, 373-375 (2011). HPTLC of red clover capsule extracts and formononetin, biochanin A, daidzein, glycitein, and genistein on silica gel, prewashed with methanol, with dichloromethane - glacial acetic acid - ethyl acetate 12:2:1 in a horizontal chamber saturated for 15 min. Quantitative determination by densitometry at 260 nm. The hRf value was 29, 34, 41, 48, and 59 for daidzein, glycitein, genistein, formononetin, and biochanin A, respectively. The two major isoflavones are formononetin and biochanin A. The limit of detection and quantification was 14 and 47 ng/band for formononetin and 12 and 40 ng per band for biochanin A, respectively. The recovery was 93.3-100.7 % for formononetin and 102.0-109.4 % for biochanin A.

J. Planar Chromatogr. 24, 376-380 (2011). HPTLC of stem bark extracts from D. melanoxylon and lupeol and betulin on silica gel, prewashed with methanol, with ethyl acetate - hexane 9:41 with chamber saturation for 3 min at 29 +/- 4 °C and 65 +/- 5 % relative humidity. The hRf value was 46 and 25 for lupeol and betulin, respectively. Quantitative determination by densitometry in absorption mode at 560 nm for lupeol and 510 nm for betulin. Detection by derivatization with 5 % methanol-sulfuric acid reagent. The LOD and LOQ was 40 and 100 ng/zone for lupeol and 50 and 100 ng/zone for betulin, respectively. The instrument precision and repeatability (n = 6) were 0.8 and 1.3 % for lupeol and 1.1 and 1.2 % for betulin, respectively. The linearity range was 100-500 ng/zone for both lupeol and betulin. The intra-day and inter-day precision was 1.1-1.7 % and 1.3-2.0 % for lupeol and 0.8-1.9 % and 1.9-2.2 % for betulin.