Proc. 9th Internat. Symp. Instr. Chromatogr., Interlaken, April 9.-11., 95-102 (1997). Overpressured layer chromatography (OPLC) can be performed as fully off-line and fully on-line, even in partition or combined techniques; variations which offer new possibilities to select the most effective technique for a given analytical or preparative task. Fully off-line OPLC is first of all an analytical method, while fully on-line and off-line/on-line OPLC are more appropriate applied for preparative purpose. HPTLC of furocumarin isomers and opium alkaloids on silica with multicomponent solvents, methyl ethyl ketone - chloroform - ether - n-hexane 128:18:27:827 for the separation of furocumarin isomers and hexane - ethyl acetate - acetone - dichloromethane - methanol - diethyl amine 200:300:300:50:27:31 in a saturated chamber and 80:60:60:10:5:6 in an OPLC chamber for opium alkaloids. Quantification by densitometry at 313 nm for furocumarin isomers and at 280 nm for opium alkaloids.

J. Chromatogr. A 903 (1/2), 211-217 (2000). Use of planar chromatography with electroosmotic flow to separate either a mixture of dyes using 80% ethanol or a mixture of miscellaneous compounds using 45% aqueous acetonitrile as mobile phase. Both mobile phases are 1.0 mM in N-[tris(hydroxymethyl)]-3-aminopropanesulfonic acid (TAPS) buffer. Presentation of the respective relationship between migration velocity and applied potential and between analysis time and distance migrated. Discussion of the merits compared to conventional TLC.

Proc. Intern. Symp. on Planar Separations Plan. Chrom. 89-109 (2003). The velocity and migration distance of the mobile-phase front in porous media, in normal TLC practice controlled by capillary forces, can be increased by application of an external electric field. The effect is observed on different TLC plates developed with non-polar and polar solvents. As a result the separation resolution of some compounds was improved. The method, a hybrid of electric forced flow and classical TLC, was named "planar dielectrochromatography" (PDEC).

J. Planar Chromatogr. 17, 411-419 (2004). A new concept, the flowing eluent walls (FEW) process, for segmentation of a non-segmented adsorbent bed, has been used for single- and multi-channel on-line overpressured-layer chromatography, which leads to active and non-active regions on the adsorbent layer during the separation process. Mobile phase only is introduced to the non-active part of the layer whereas mobile phase and sample can be admitted to the active parts. The FEW concept provides the possibility of real multichannel liquid chromatographic separation on a non-segmented layer and column shaped adsorbent bed. Separation of chamomille oil, dye mixtures, ascorbigen standards, and cabbage extracts, were used as examples. The FEW configuration is suitable for rapid isolation of relatively large amounts of a substance.

Biomed. Chromatogr. 21 (1), 94-100 (2006). Presentation of a post TLC developing technique to detect substances which can inhibit tyrosinase activity. The TLC plate is sprayed with tyrosinase and l-tyrosine solutions successively. A positive result is detected as white zone against a brownish-purple background. The method is suitable as a quick screening procedure for tyrosinase inhibitor detection, and as a guiding procedure for the isolation of tyrosinase inhibitors from mixtures or natural product extracts.

J. Planar Chromatogr. 27, 240-244 (2014). HPTLC of sulfide ions derivatized with 4-[p-,Ndimethylamino) phenyl]-2,6-diphenylpyrylium cations (25 μmol) in acetonitrile) on silica gel with a mixture of phosphoric buffer (pH 3.0) - propan-2-ol - acetonitrile 8:8:1. Quantitative determination by scanning and image analysis. The hRF values for thyopyrylium and the derivatization reagent were 73 and 54, respectively. Linearity was in the range of 40-500 pmol/zone. The intermediate/interday/intra-day precisions were below 2 % (n=9). The LOD and LOQ were 11 and 33 pmol/zone, respectively. Recovery was between 98 and 108 %.

J.A.O.A.C. 69, 499-503 (1986). Improvement of a spray reagent for TLC identification of uric acid: aqueous solution of ferric chloride and potassium ferricyanide, requiring neither heating nor pH control. Comparison of specificity and sensitivity to 5-10 ng of uric acid with those of other sprays. The false negative rate (at 95 % confidence interval) is 0-9.7 % for this spray compared with 0.7-18.7 % for the others.

J.Chinese Herb Med. (Zhongcaoyao) 21, 18 (1990). TLC of glycyrrhizin on silica with butanol - acetic acid water 4:1:2. Detection under UV 254 nm. Quantification by densitometry at 254 nm.