J. Planar Chromatogr. 18, 336-343 (2005). HPTLC of thirty-three compounds with benzodiazepine properties on silica gel after prewashing first with methanol and then with dichloromethane - methanol 19:1 in a saturated horizontal chamber and three optimized mobile phases: dichloromethane - methanol 19:1, ethyl acetate - cyclohexane - 25 % ammonia 50:40:0.1, and in a third run cyclohexane - acetone - methyl t-butyl ether 3:2:1. Diode-array HPTLC makes it possible to identify all the compounds with high certainty down to a level of 20 ng. An algorithm for spectral recognition which is combined with Rf values from the three separation steps into one fit factor is presented. This set of data is unique for each of the compounds investigated and enables unequivocal identification.

Chromatographia (Suppl.) 28, 29-31 (1989). Description of a procedure of photographing thin-layer plates in UV 254 and 366 nm. Achievement of professionally accurate documents of TL chromatograms by using commercially available single-lens reflex cameras, selected negative films, an approved UV-filterset and the pertinent experienced shutter speed.

J. Planar Chromatogr. 10, 258-262 (1997). Photoacoustic spectroscopy (PAS) was applied to investigate the in-depth distribution of compounds inside the sorbent on a TLC plate. The PAS was also used to obtain unknown values of thermal diffusivity for investigated TLC plates which are essential for the determination of thermal diffusion lengths and layer thickness that are probed at a certain modulation frequency of the laser excitation beam. The PAS results revealed nonuniform concentration distribution of compounds inside the sorbent which arise mainly from the secondary chromatography inside the sorbent during the process of drying. Also published in Proc. 9th Internat. Symp. Instr. Chromatogr., Interlaken, April 9.-11., 353-363 (1997).

J. Chromatogr. Sci. 21, 190-192 (1983). TLC of 3H-lysine,-leucine, -uridine, -thymidine, met-enkephalin on silica, cellulose and PEI-cellulose.

Chromatographia 18, 23-27 (1984). The Michaelis-Menten function describes a non-linear relationship and is a possible calibration curve in TLC. Usually the linearized forms are used but the problem of uncontrolled error propagation arises from data transformation and hence incorrect calibration. Non-linear regression analysis is therefore used in this paper. The results of erroneous transformation according to Lineweaver-Burk and to Eadie are compared with the results of non-linear regression by means of three sets of measured data or data given in the literature.

J. Chromatogr. 392,464-469 (1987). TLC and OPLC of steroid isomers on silica and on amino-bonded silica with 1) chloroform - ether - MEK 4:3:3, 2) n-hexane - MEK - diethylamine 8:1:1, and 3) chloroform - acetone 9:1. Measurement by densitometry at 254 nm. Also, investigation of the applicability of different spray reagents on amino-bonded silica.

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.

Proc. 6th Int. Symp. Instrum. Planar Chromatogr., (Interlaken 1991), Inst. Chromatogr., Bad Dürkheim, FRG, 231-234 (1991). The sample preparation system includes an OPLC chamber as an interface where samples of interest are migrated toward the column of an HPLC system. Another way of clean-up is the combination of conventional TLC with OPLC transfer. According to the chromatographic properties of unwanted sample materials, the impurities in front and/or starting zone can be eliminated while analyzable compounds from the localized area of the layer can be transferred to the HPLC system.