Food Chem. 79, 337-342 (2002). HPTLC of polyphenol compounds (caffeic acid derivatives, quercetin and kaempferol glycosides) in the leaves of Lactuca sativa on RP-18 with water – methanol – acetic acid 25:25:3. Detection by dipping into a solution of 1 % ethanolamine diphenylborate in methanol for 24 h. Quantitative determination by absorbance measurement at 365 and 440 nm. The total flavonoid amount is expressed as isoquercitrin using a three point regression curve in the range of 1 and 5000 ng/zone.

J. Liq. Chromatogr. Relat. Technol. 30, 2267-2285 (2007). Analytical and preparative TLC of lipid classes, their fatty acid profiles, and the triacylglycerol and sterol composition on silica gel and modified silica gel (impregnated with silver nitrate for Ag-TLC or dimethyldichlorosilane for RP-TLC). TLC of lipid reference mixture on silica gel with hexane - acetone 25:4. Detection by spraying with 50 % ethanolic sulfuric acid and heating at 200 °C. Preparative TLC for isolation and quantification, followed by detection under UV light, spraying the edges with 2’,7’-dichlorofluorescein, scraping off, elution with diethyl ether and weighting. Quantitative Ag-TLC (impregnated by dipping into 0.5 % or 2 % methanolic solution of silver nitrate) followed by detection with bromine and sulfuryl chloride vapor for 30 min each, followed by heating at 180-200 °C. Preparative Ag-TLC with 4 different mobile phases. Quantitative RP-TLC on Kieselguhr treated for 6 h with vapors of dimethyldichlorosilane and washed with methanol using acetone - acetonitrile - water. Quantitative determination by absorbance measurement at 450 nm.

J. Planar Chromatogr. 22, 97-100 (2009). TLC of (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, theaflavin, theaflavin 3-gallate, theaflavin 3’-gallate, and theaflavin 3,3’-digallate on polyamide phase in a horizontal chamber (saturated for 15 min) by twofold development with chloroform - methanol 2:3 or n-butanol - acetone - acetic acid 5:5:3. Separation of the flavonols myricetin, quercetin, kaempferol, rutin and the phenolic acids gallic acid, chlorogenic acid, and caffeic acid was achieved by twofold development with chloroform - methanol 2:3. Detection by spraying with iron(III) chloride solution and evaluation under daylight. Quantitative determination by absorbance measurement at 600 nm.

Anal. Chim. Acta 624 (1), 1-15 (2008). Aminoglycosides and macrolides are important antibiotics for veterinary medicine and are widely used in the treatment of bacterial disease, and as feed additives for growth promotion. As a result the European commission set strict criteria for monitoring residues and requires testing for low levels of aminoglycosides and macrolides in foods. Therefore the development of fast, reliable, and sensitive methods for the extraction and subsequent analysis of these antibiotics is of great interest. The review discusses analytical methods for both extraction and determination of antibiotics in various food matrices focusing on the last 10 years. Extraction and clean-up methods such as deproteinization and solid-phase extraction are described, and various screening methods including TLC, EI, CE, microbiological assays, and LC combined with MS are reviewed.

Quim. Nova 33, 43-47 (2010). HPTLC of aflatoxin B1 in peanuts on silica gel with chloroform - acetone 99:1. Quantitative determination by absorbance measurement at 366 nm, using a CCD camera followed by image processing using the software ImageJ. Linearity was between 0.8 and 4.8 ng/zone. The intra-day and inter-day precisions had a RSD lower than 5.2 %. LOD was 0.4 ng/zone while LOQ was 1.2 µg/kg. The average recovery was 94.9 %. The proposed method is a simple, efficient and low cost tool for quantitative analysis of aflatoxin B1 in peanut samples.

J. Sep. Sci. 33, 3794-3799 (2010). HPTLC of caffeine (1), theobromine (2) and theophylline (3) in different types of tea on silica gel with chloroform - dichloromethane - isopropanol 4:2:1. Quantitative determination by absorbance measurement at 254 nm. The hRF of (1), (2) and (3) was 65, 45 and 56, respectively. Limits of detection and quantification were 22 and 45 ng for (1), 23 and 46 ng for (2) and 22 and 43 ng for (3), respectively. The intra-day and inter-day precisions had a %RSD lower than 2.55 % (n=6) for all substances. Recoveries (by standard addition) were between 95.1-101.5 % for all the three methylxanthine derivatives. The values of LOD and LOQ obtained are similar with those obtained by HPLC.

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.

The case of determination of rosmarinic acid in different matrices. J. Chromatogr. A 1220, 156-161 (2012). Description of a new method for determination of rosmarinic acid in different matrices by HPTLC on silica gel with toluene – ethyl formate – formic acid 6:4:1. Quantification by densitometry in absorbance mode at 330 nm. The influence of the main HPTLC operative parameters was figured out in view of a more stringent validation process. Together with the fundamental HPTLC instrumentation an automatic developing chamber is mandatory as it allows for control of the relative humidity and the saturation conditions and thus assures reproducibility. Several commercial preparations containing rosmarinic acid in different amounts were tested and rosmarinic acid in the range of 132-660 ng/band was found. The %RSD of repeatability and intermediate precision did not exceed 2.