Acta Chromatographica 20(4), 685-695 (2008). Determination of p-coumaric and protocatechuic acids in an ether fraction from a methanolic extract of Aquilegia vulgaris L. by HPTLC on silica gel with mixtures of heptane, dichloromethane, diisopropyl ether, formic acid, and water in various ratios. Satisfactory separation of the phenolic acids was achieved by use of the multiple gradient development technique. HPTLC results of the quantities of p-coumaric and protocatechuic acids were somewhat higher (0.396 and 2.584 mg/g dry plant material, respectively), than those determined by HPLC (0.374 and 2.283 mg/g dry plant material, respectively). Both methods were satisfactory in the precision, expressed as relative standard deviation, and are useful for quality control of Aquilegia vulgaris extracts.

J. of Chromatogr. A 1218 (19), 2820-2825 (2011). A unified procedure for image preprocessing of 2D TLC videoscans saved as JPG files is proposed for further supervised or unsupervised chemometric analysis. The procedure was based on open source software and included denoising using a median filter, baseline removal with the rollerball algorithm and nonlinear warping using spline functions. The application of the proposed procedure enabled filtration of random differences between images, such as changes in the intensity of the background as well as differences in the location of the zones. After the preprocessing only the zone intensity had an influence on the statistical analysis by principal component analysis (PCA) or other techniques. The proposed technique was successfully applied for the determination of the differences between three Carex species based on the 2D videoscans of the extracts.

J. AOAC Int. 93, 1757-1767 (2010). HPTLC of four mixtures of 21 pesticides on RP-18 by PPEC under different operating conditions. The samples were separated on a prewetted RP-18 phase with acetonitrile - buffer. Detection under UV light at 254 or 366 nm and in the range of 197 to 1033 nm with a DAD densitometer. Reproducible retention of pesticides was obtained; the reported separations are over 10 times faster than the corresponding separations by TLC.

Quim. Nova. 35, 541-545 (2012). HPTLC of isoorientin on silica gel with ethyl acetate - formic acid - water 9:1:1. Detection by dipping into a solution of diphenylboric acid-2-aminoethyl ester (100 mg) and PEG 400 (500 mg) in methanol (10 mL). Quantitative determination by fluorescence measurement at 366 nm. The HPTLC method (120 min) was almost seven times faster than the HPLC method (700 min). The amount of solvent consumed in the HPTLC method (12 mL) was almost eight-fold less than that used in the HPLC method (98 mL), indicating that HPTLC is an alternative technique for analyzing large numbers of samples.

J. Planar Chromatogr. 26, 43-55 (2013). TLC of cefditoren pivoxil on silica gel with 1-butanol - acetic acid - water 17:2:1. Quantitative determination by absorbance measurement at 295 nm. The hRf of cefditoren pivoxil was 70. Linearity was in the range of 600-1600 ng/zone. The LOD and LOQ were 40 and 130 ng/zone, respectively. Recovery (by standard addition) was between 97.8 and 101.8 %. Intermediate/interday/intra-day precision was below 2 % (n=3). The method showed comparable results with a validated HPLC method.

J. Planar Chromatogr. 27, 466-471 (2014). HPTLC of (1) flumethasone pivalate, (2) flumethasone, and (3) clioquinolon on silica gel with benzene – hexane – acetone – formic acid 500:400:200:13. Quantitative determination by absorbance measurement at 235 nm. The hRF values of (1) to (3) were 31, 7 and 64, respectively. Linearity was in the range of 30-400 ng/zone for (1), 50-300 ng/zone for (2) and 150-500 ng/zone (3). The intermediate precision was below 2 % (n=3) for (1) to (3). The LOD and LOQ were 9 and 27 ng/zone for (1), 13 and 39 ng/zone for (2) and 41 and 123 ng/zone for (3). Recoveries for (1) to (3) were in the range of 90-110 %. The method was statistically compared to a validated HPLC method.

CBS 113, 13-15 (2014). HPTLC of glycosylceramide Glc-d18:2 h16:0 from wheat germ and standards squalene, cholesteryl oleate, glyceryl trioleate, linoleic acid, ß-sitosterol, and ß-sitosterol glucoside on silica gel in the AMD 2 with a 18-step gradient modified from Opitz et al. (Chromatographia 73 (2011) 559), methanol replaced ethanol, and the mobile phase composition was changed slightly (pre-conditioning with 4 M acetic acid before each step, drying time 1.5 min, development duration 3 h and solvent consumption 200 mL). Detection by dipping in copper sulfate phosphoric acid reagent for 20 s and heating at 130 °C for 15 min revealed grey-brown bands. Densitometry evaluation by absorbance measurement at 546 nm. For Glc-d18:2 h16:0, regression analysis showed a polynomial relationship with coefficients of determination (R2) from 0.995 to 0.999 (n=3, 50 - 1000 ng/band). LOD (S/N 3) and LOQ (S/N 10) of Glc-d18:2_x000D_ h16:0 were 10 ng/band and 50 ng/band, respectively (n = 6).

J. Chromatogr. A 1534, 179-187 (2018). Investigation of the influence of pH of the mobile phase buffer on retention of peptides in both normal phase (NP) and reversed phase (RP) HPTLC systems with C18 silica-based adsorbent as the solid phase. Comparison of the influence of pH on retention and/or migration distance of peptides in separation systems of HPTLC and pressurized planar electrochromatography (PPEC) techniques. It was found that the change of pH of the mobile phase buffer can be used for two-dimensional HPTLC separation of peptides, but much stronger change of separation selectivity can be achieved by overall inversion of separation system type (NP/RP). Influence of the mobile phase pH on selectivity of peptide separation in PPEC is different than that in HPTLC, due to the significant share of electrophoretic effect in mechanism of separation and better selectivity of separation by PPEC, however the change of pH affects the efficiency of the separation system in both techniques, so it can be used for optimization of separation conditions. Discussion of some modifications of PPEC equipment and materials useful for application of this technique in the field of peptide analysis.