J. of Chromatogr. A 1218 (20), 3089-3084 (2011). Comparison of the separation of the structurally related angiotensin-converting enzyme (ACE) inhibitors lisinopril, cilazapril, ramipril and quinapril and their corresponding active diacid forms (prilates) by conventional TLC on silica gel with the separation on monolithic ultra-TLC (UTLC) phase. Technical modifications of the commercially available equipment for sample application, development and detection were necessary for the use with UTLC plates. Development in a modified horizontal developing chamber with ethyl acetate - acetone - acetic acid - water 16:4:1:2. Detection by absorbance measurement at 220 nm and after exposure to iodine vapors under daylight, as well as by image analysis. As a result the monolithic layer was more efficient for the separation of structurally similar polar compounds, such as prilates, than conventional silica layers. Confirmation of the identity of the compounds by ESI-MS after their online extraction from the UTLC and TLC plates.

J. Liq. Chromatogr. Relat. Technol. 35, 1415-1428 (2012). HPTLC of prometryn in wine samples on silica gel with tetrahydrofuran - n-heptane 1:4 in the first direction and with methanol - water 7:3 in the second direction after the plate was turned by 90°. Quantitative determination by absorbance measurement at 223 nm. The hRf value of prometryn was 35. Linearity was in the range of 220-1320 ng/zone. Limits of detection and quantification were 110 and 330 ng/zone. The method was compared with a validated HPLC-DAD method and both methods are useful for correct identification of pesticides in complicated mixtures.

J. Planar Chromatogr. 25, 138-144 (2012). HPTLC of diosmin (1) and hesperidin (2) on silica gel with ethyl acetate - methanol - water - acetic acid 25:2:2:1. Quantitative determination by absorbance measurement at 330 nm. Linearity was in the range of 100-3000 ng/zone for (1) and 250-7500 ng/zone for (2). The method did not show any statistically significant deviation when compared with a validated HPLC.

J. Planar Chromatogr. 27, 29-32 (2014). HPTLC of rhein in the pulp of Cassia fistula on silica gel with ethyl acetate - methanol - water 100:17:10. Quantitative determination (1) by TLC image analysis using a flatbet scanner and (2) by absorbance measurement at 435 nm. The hRF value for rhein was 49. Linearity was in the range of 400-1200 ng/zone for (1) and 29-230 ng/zone for (2). The intermediate/interday/intra-day precisions were below 3 % (n=3). The LOD and LOQ for rhein were 85 and 257 ng/zone for (1) and 3 and 11 ng/zone for (2). Mean recovery was 102.3 % for (1) and 101.2 % for (2).

J. Planar Chromatogr. 28, 115-118 (2015). TLC of 35 compounds on RP-18 and cyano phase with six modifiers (acetonitrile, acetone, dioxane, propan-2-ol, methanol, and tetrahydrofurane). The extrapolated Rm data were recomputed and compared to HPLC results with 2 modifiers. HPLC (in gradient mode) and TLC perform in comparable manner in the lipophilicity assessment of the investigated model compounds. With its simplicity, it is a strong argument to use TLC in lipophilicity studies.

J. Planar Chromatogr. 30, 340-349 (2017). HPTLC of aripiprazole and its nine impurities as well as ziprasidone and its five impurities on RP-18 with methanol (1) or ethanol (2) as organic modifiers in the mobile phase. When methanol was used as organic modifier, the mobile phase with the lowest content of methanol was methanol – water – ammonia solution 25 % 13:6:1 and the mobile phase with the highest content of methanol was methanol – water – ammonia solution 25 % 17:2:1. When ethanol was used as organic modifier, the mobile phase with the lowest content of ethanol was ethanol – water – ammonia solution 25 % 12:7:1 and the mobile phase with the highest content of ethanol was ethanol – water – ammonia solution 25 % 16:3:1. Lipophilicity was estimated to develop the quantitative structure–retention relationship (QSRR) models which enabled fast and reliable prediction of the retention behavior.

(TLC and HPLC in mycotoxin analysis.) Fresenius Z. Anal. Chem. 318, 281-282 (1984). TLC of aflatoxins and patulin on different layers with various solvent systems. Detection by fluorescence.

J. Chromatogr. Sci. 22, 538-547 (1984). Principal component analysis (PCA) with Rf values for 596 basic and neutral drugs in 4 eluent mixtures on silica. Two-component model explaining 77 % of the total variance. Each drug is characterized on a plane by two principal component scores. For the identification of unknowns the method provides a drastically reduced short list of possible candidates. The 4 eluent systems are: a) methanol - NH3 100:1.5, b) cyclohexane - toluene - diethylamine 75:15:10, c) chloroform - methanol 9:1, d) acetone.