CBS 100, 13-15 (2008). HPTLC of caffeine on silica gel with ethyl acetate - methanol - 25 % ammonia 90:15:1 (for samples of energy drinks) or chloroform - ethanol - 37 % acidic acid - acetone - water 54:27:10:2:2 (for samples of headache tablets). Detection under UV 254 nm. Quantitative determination by absorbance measurement at UV 274 nm. Automated online extraction with an HPTLC/MS interface connected to a ESI mass spectrometer. Without any internal standard the caffeine mass signal was recorded in the selected ion monitoring mode at m/z 195 [M+H]+. The method was validated. Repeatability was 5.6 % (%RSD, n=6) and reproducibility of the plate mean value was 1.5 % (%RSD, n=3).

Anal. Bioanal. Chem. 389, 827–834 (2007). A total extract of hen egg yolk is used as phospolipid mixture to demonstrate the capabilities. TLC of phosphatidylcholine, lysophosphatidylcholine, sphingomyelin, phosphatidylethanolamine, lysophosphatidylethanolamine and phosphatidylinositol on silica gel with chloroform - ethanol - water - triethylamine 5:5:1:5. Detection under UV 366 nm after spraying with primuline (Direct Yellow 59) reagent. Direct coupling MALDI-TOF MS and TLC can be easily implemented on commercially available MALDI-TOF devices. Roughly clean spectra without major contributions from fragmentation products and matrix peaks were obtained. This approach was sensitive enough to detect the presence of phospholipids at levels of less than 1 % of the total extract.

J. Agric. Food Chem. 55, 7489-7494 (2007). HPTLC of fruit powder and commercial products of Noni (Morinda citrifolia) on silica gel with chloroform – methanol 9:1 or chloroform – methanol – water 13:6:1. Detection under UV 254 and 366 nm after spraying with vanillin reagent (1 % vanillin in ethanol containing 2 % sulphuric acid), followed by heating at 105 °C. The following compounds were identified as markers (hRf): ursolic acid (60), linoleic acid (55), scopoletin (53), 3-methyl-1,3-butanediol (27).

J. Chromatogr. A 1217 (23), 3702-3706 (2010). Evaluation of the chromatographic behavior of some artificial and natural sweeteners by HPTLC on RP18, RP18W, RP8, cyano and amino phases with mixtures of acetonitrile - water in different volume proportions. The lipophilicity is given through chromatographic descriptors such as RM0, mean of RM (mRM), and scores of RM values corresponding to the first principal component (PC1/RM). In addition, scores and loadings resulting from covariance matrix of retention data provide new information about similarity and differences of investigated compounds and between the stationary phase and the mobile phases. The experimental lipophilicity indices estimated from retention data were correlated with computed values, via computer software and internet module. Results were in accordance at a highly significant statistical level.

J Food Sci Technol 46(2), 114-117 (2009). A method for isolation and analysis of the artificial sweetener sucralose from the Indian sweet Burfi has been developed. For the isolation samples were suspended in water, treated with K3Fe(CN)6 solution and zinc sulfate, and filtrated. Semi-quantitative HPTLC analysis on amino layer with acetonitrile - water 4:1. The developed plate was heated at 190 °C for 20 min and spots were detected under UV 365 nm. Treating the plate with 5 % methanol CTMA increased the sensitivity (25 ng/zone). Quantitative HPTLC on silica gel with dichloromethane - methanol 4:1. Detection by spraying with 15 % methanolic sulfuric acid and heating at 100 °C for 10 min. The spot density was evaluated with Bio-rad fluorescence imaging software and confirmed by comparison with the standard. The method was linear in the range of 0.5-1.25 µg/band.

J. Planar Chromatogr. 24, 113-115 (2011). TLC of dichlorvos on silica gel with cyclohexane - acetone - methanol 16:6:1. Detection by spraying with 2 % sodium hydroxide solution and subsequent spraying with 2 % thiobarbituric solution followed by heating at 90 °C for 10 min. The hRf of dichlorvos was 50. The limit of detection was approximately 18 µg/zone. Spectrophometric analysis of dichlorvos was performed by measuring the absorbance of the sample solution. The linearity was in the range of 50-350 µg/mL dichlorvos. On alkaline hydrolysis dichlorvos forms dimethylphosphoric acid and dichloroacetaldehyde; the latter reacts with 2-thiobarbituric acid to give a sharp pink spot. The reagent is selective for dichlorvos, and does not react with other organophosphorus, organochlorine, carbamate, and synthetic pyrethroid insecticides.

J. Liq. Chromatogr. Relat. Technol. 34, 920-927 (2011). TLC of flumequine in milk on silica gel with dichloromethane - methanol - 2-propanol - 25 % aqueous ammonia 3:3:5:2. Bioautography by dipping into an Escherichia coli bacteria suspension for 5 h at 37 ºC. After incubation, the plates were sprayed with 0.2 % MTT ([3-(4,5-dimethyldiazol-2-yl)-2,5 diphenyltetrazolium bromide] aqueous solution and incubated for about 30 min at 37 ºC. The new procedure gave better recoveries of flumequine residues from milk compared with the previous method.

Clean-up of matrix-rich samples using high-troughput planar solid phase extraction (HTpSPE). Black and green tea samples were spiked with 7 pesticides (acetamiprid, azoxystrobin, chlorpyrifos, fenarimol, mepanipyrim, penconazole, and primicarb) at level 0.01, 0.1 and 1 mg/kg. Extraction with acetonitrile, pre-cleaning by dispersive SPE. TLC on silica gel (prewashed with acetonitrile) of samples applied as rectangles of 3 x 16 mm first with acetonitrile - water 19:1 over 85 mm and after drying for 5 min with acetone - water 7:1 in the opposite direction over 31 mm. Detection under UV 254 and 366 nm and by dipping in primuline reagent (0.2 % in acetone - water 4:1) and detection under UV 366 nm and white light. Elution of target zones into autosampler vials by TLC-MS Interface with acetonitrile - 10 mM ammonium formate buffer 1:1, flow rate 0.2 mL/min. After clean-up the samples are free of caffeine which interferes with pesticide detection.