Anal. Chem. 77, 4385-4389 (2005). TLC of caffeine on RP-8 with methanol – water (73) followed by heating at 110 °C for 15 min). Detection at 214 nm. Quantification of caffeine at the low-nanogram level is performed directly from the RP-8 TLC plate using a surface sampling probe and an ESI mass spectrometry system employing selected reaction monitoring detection, and a deuterium-labelled internal standard spotted with the samples. TLC/ESI-MS/MS successfully allowed caffeine quantification in six commercially available beverages using only minimal sample preparation. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 µm/s. A 50-fold linear range of the TLC/ESI-MS/MS procedure (1.0 - 50 ng/zone of caffeine) was given. The estimated limit of detection was 1.0 ng/zone. Spike recoveries with standards and real samples ranged between 97 and 106%. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts were consistently 8 % higher than the literature values.The surface sampling probe used was restricted to unpolar layers.

Anal. Bioanal. Chem. 392, 849-860 (2008). HPTLC of cell lipids on silica gel with chloroform - ethanol - water - triethylamine 5:5:1:5. Detection under UV 366 nm after spraying with primuline (Direct Yellow) reagent. Coupling with MALDI-TOF-MS which is traditionally used for proteomics, but is also a useful tool for lipid analysis. Depending on the applied matrix, however, some lipid classes are more sensitively detected than others and this may even lead to suppression effects if complex mixtures are analyzed. Therefore, a previous separation into the individual lipid classes is necessary. Using artificial lipid mixtures or easily available tissue extracts, it has already been shown that lipids can be conveniently analyzed by MALDI-TOF MS directly on the TLC plate. An initial TLC-MALDI-TOF-MS study of the lipid composition of ovine mesenchymal stem cells is presented. Due to the complex composition of these cells, data are also compared to lipids extracted from human erythrocytes. Even very minor lipid classes can be easily detected and with much higher sensitivity than by common staining protocols.

Anal. Chem. 81, 8426-8433 (2009). HPTLC of zeaxanthin, cryptoxanthin, beta-carotene, lutein and pollen extracts on silica gel with tetrahydofuran - methylene chloride - n-hexane by automated multiple development. Quantitative determination by absorbance measurement at 425 nm, which has to be accomplished within 5 min after development due to the fast bleaching of the carotenoid color. The analysis of carotenoids in pollen extracts was confirmed by resonance Raman data measured directly on the HPTLC plates.

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.

Chinese J. of Spectroscopy & Spectral Anal. 34 (4), 990-993 (2014). In recent years, some frauds were discovered on the drug market, e.g. chemical drugs with similar effect were illegally added to herbal TCM for hypertension which may cause a variety of adverse reactions and even endanger life. To ensure the safety of patients a method is presented for rapid screening of antihypertensive drugs. TLC on silica gel with dichloromethane – methanol – water 90:10:1, detection under UV 254 nm. Identification of nicardipine hydrochloride, doxazosin mesylate, propranolol hydrochloride and hydrochlorothiazide by comparison of the corresponding hRf values of standards. Qualitative analysis of the sample target zones by adding a few drops of silver glue solution onto each zone and then detection by surface enhanced Raman spectroscopy (SERS) using a portable Raman spectrometer at the integration time of 10 s and the laser power of 100 mW with a minimum detection amount of 5, 5, 50 and 50 ng, respectively. The TLC method was optimized regarding mobile phase, sample application volume, the concentration of silver glue solution, etc. The method was used for the analysis of 10 commercial products from the drug market. Two products contained illegally added nicardipine hydrochloride and doxazosin mesylate, and one product contained propranolol hydrochloride and hydrochlorothiazide.

by the combination of high-performance thin-layer chromatography with direct bioautography and mass spectrometry. J. of Chromatogr. A 1422, 310-317 (2015). Investigation of two tansy (Tanacetum vulgare L.) essential oils, obtained by steam distillation of the capitula with subsequent liquid-liquid extraction (oil 1) or with use of an auxiliary phase for the trapping of the steam components (oil 2), against Bacillus subtilis F1276, B. subtilis spizizenii (DSM 618), Xanthomonas euvesicatoria, Pseudomonas syringae pv. maculicola, Ralstonia solanacearum strain GMI1000 and Aliivibrio fischeri by using the coupling of HPTLC to direct bioautography (HPTLC-DB). Oil 2 was richer in components and provided more inhibition zones due to the advanced extraction process. Identification of the main bioactive components by scanning HPTLC-direct analysis in real time mass spectrometry (HPTLC-DART-MS) and solid-phase microextraction GC electron impact MS (SPME-GC-EI-MS) as cis- and trans-chrysanthenol as well as trans-chrysanthenyl acetate. The results indicated that cis-chrysanthenol exhibited antibacterial effects against all tested bacteria. Trans-chrysanthenol inhibited B. subtilis, R. solanacearum and A. fischeri, and trans-chrysanthenyl acetate was an inhibitor for X. euvesicatoria, R. solanacearum and A. fischeri. However, the ionization characteristics and the recorded mass spectra showed that DART is a softer ionization technique than EI and more affected by ambient conditions and thus prone to additional oxidation products, although HPTLC-DART-MS resulted in a comparable fragmentation.

Planta Medica 83(03/04), 300-305 (2017). Preparative TLC on 1) RP-18 phase with methanol – water, in several proportions from 2:1 to 9:11 and on 2) silica gel with dichloromethane – ethyl acetate, from 5:1 to 10:3 was applied to purify eight phenylethylchromones from subfractions of a methanolic extract of Aquilaria filaria agarwood. Preparative TLC on silica gel with n-hexane – ethyl acetate 2:1 was also used to separate the products of one of these chromones (2-(2-hydroxy-2-phenylethyl)-4H-chromen-4-one) with the (S)- and (R)-MTPA-Cl (α-methoxy-α-trifluoromethyl-phenylacetyl-chloride) needed for the Mosher ester method for asymmetric carbon configuration, allowing, after NMR, the determination of the chromone as an uneven mixture of R- and S-enantiomers (4:1). The enantiomer separation was done after derivatisation into diastereoisomers (no chiral separation).

J. Sep. Sci. 41, 4387-4393 (2018). A new separation layer for TLC plates was developed for the separation in thin layers and direct conjugation to matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) without additional sample preparation. Best results were obtained with layers containing 19 to 29 % glycidyl methacrylate in the initial polymerization mixture.