CBS 113, 9 (2014). HPTLC of caffeine in energy drinks (applied neatly without sample preparation) on silica gel MS-grade with 2-propanol – n-heptane – water 7:3:1. Detection under UV 254 nm and by dipping into anisaldehyde reagent. Quantitative evaluation by absorbance measurement at 273 nm. The hRf of caffeine was 55. For confirmation of results, zones were eluted with the TLC-MS Interface (acetonitrile – water 19:1 with 0.1 % formic acid, flow rate 0.1 mL/min) and directly transferred to a mass spectrometer and measured in ESI(+) full scan mode (m/z 100 – 500).

J. Liq. Chromatogr. Relat. Technol. 39, 271-276 (2016). HPTLC of ziprasidone and its impurities on silica gel with toluene – methanol – glacial acetic acid 15:1:1. Quantitative determination by absorbance measurement at 250 and 320 nm. The hRF value was 42 for ziprasidone and 19, 28, 31, 58 and 70 for its impurities. LOQ of impurities was 25 ng/zone. Recovery was between 94.9 and 106.7 %. See also J. Planar Chromatogr. 29, 239-246 (2016).

fruits. J. Planar Chromatogr. 29, 356-360 (2016). HPTLC of gallic acid (1), vanillic acid (2), protocatechuic acid (3), and quercetin (4) in the fruits of Limonia acidissima on silica gel with toluene – ethyl acetate – formic acid 5:4:1. Quantitative determination by absorbance measurement at 254 nm. The hRF values of (1) to (4) were 30, 47, 37 and 42, respectively. Linearity was between 100 and 600 ng/zone for (1) to (4). The intermediate precisions for (1) to (4) were below 1.6 % (n=3). The LODs and LOQs were 30 and 91 ng/zone for (1), 25 and 76 ng/zone for (2), 33 and 100 ng/zone for (3) and 28 and 85 ng/zone for (4). Recoveries were between 98.0 and 100.1 % for (1) to (4).

J. Chromatogr. Sci. 54 (1), 58-63 (2016). Description of a method for simultaneous determination of the two monoterpenes menthol and eucalyptol, contained in several analgesic pharmaceutical formulations for external use, by HPTLC on silica gel with hexane – ethyl acetate 4:1. The hRF value of menthol was 34 ± 4 and of eucalyptol 56 ± 4. Linearity was between 100–800 ng/zone (r2 = 0.9979) for menthol and 52–1107 ng/zone (r2 = 0.9937) for eucalyptol.

J. Chromatogr. Sci. 54 (7), 1077-1083 (2016). Development of a method for phenolic profiling in the assessment of authenticity of poplar-type propolis by comprising HPTLC, image processing and chemometric approach. TLC fingerprinting by applying modern TLC equipment in combination with software for image processing, pattern recognition by using the principal component analysis. Characterization of phenolic profile was performed along with the determination of the botanical and geographical origin of propolis. The results revealed that Central and Southeastern European propolis samples are rich in flavonoids, and phenolic compounds proved to be suitable markers for the determination of European propolis authenticity.

J. Planar Chromatogr. 30, 199-204 (2017). HPTLC of sophoridine (1), matrine (2), and sophocarpine (3) in S. alopecuroides on silica gel with toluene – acetone – methanol – ammonia – water 80:30:2:5:80. Detection by spraying with bismuth potassium iodide reagent (1:1 mixture of 0.85 g of bismuth nitrate with 10 mL of glacial acetic acid and 40 mL of water, heated for dissolution, and 8 g of potassium iodide in 30 mL of water). Quantitative determination by absorbance measurement at 500 nm. The hRF values for (1) to (3) were 22, 56 and 65, respectively. Linearity ranged from 415-2491 ng/zone for (1), 424-2547 ng/zone for (2) and 410-2460 ng/zone for (3). The intermediate precision was <5 % (n=3). Recovery rate ranged from 97.8 to 98.9 % for (1), 98.3 to 100.9 % for (2) and 99.1 to 101.2 % for (3).

J. Liq. Chromatogr. Relat. Technol. 40, 467-478 (2017). HPTLC of lisinopril (1), amlodipine (2), valsartan (3) and hydrochlorothiazide (4) in pharmaceutical formulations and in human plasma on silica gel with methanol – dichloromethane – glacial acetic acid 90:10:1. Quantitative determination by absorbance measurement at 215 nm. The hRF values for (1) to (4) were 29, 56, 67 and 75, respectively. Linearity was between 400 and 2000 ng/zone for (1), 200 and 1500 ng/zone for (2), 1000 and 7000 ng/zone for (3) and 300 and 1500 ng/zone for (4). LOD and LOQ were 83 and 252 ng/zone for (1), 54 and 164 ng/zone for (2), 156 and 474 ng/zone for (3) and 77 and 234 ng/zone for (4), respectively. The intermediate precision was <3 % (n=6). Recovery rate ranged from 99.3 to 100.9 % for (1-4).

J. Chromatogr. A 1509, 147-152 (2017). Presentation of proper sigmoidal dose-response curves which can be linearized by the logit function resulting in logit-log plots in semi-log plots, from a planar yeast estrogen screen (pYES) as known for the evaluation of enzyme-linked immunosorbent assays and radioimmunoassays in microtiter plates. It was assumed to obtain sigmoidal shaped dose-response curves from the measured sign plots because pYES represents the transfer of the receptor assay YES to HPTLC. As no typical sigmoidal curves were obtained when peak areas were plotted against the applied amount on a logarithmic scale, peak heights were examined in the present study, which revealed proper dose-response curves when plotted against the log amount. The presence of sigmoidal dose-response curves from HPTLC-pYES made it possible to transform the signals into logits and, therefore, to create logit-log plots with linear correlations. The working range was up to 500 pg/zone for both 17β-estradiol (1) and 17α-ethinylestradiol (2). The mean recovery by applying logit-log plots for (1) and (2) from spiked water samples (2-20 ng/L) were 90 % and 108 %, respectively, with %RSD≤24 %. Determination of the half maximal effect dose (ED50) of the estrogen active compounds, which was represented by the intersection of the linear graph with the abscissa and also determination of the estrogenic potential in terms of estradiol equivalent factors by using the ED50 values, resulting in 0.64 for (2).