CBS 125. HPTLC of estrogen-active compounds in a migrate of a food contact material on silica gel with chloroform - acetone - petroleum ether 11:4:5. Planar Yeast Estrogen Test (P-YES) was performed by spraying 2 mL yeast cells onto HPTLC plates, followed by incubation at 30 °C for 3 h and spraying with 2 mL 0.5 mg/mL 4-methylumbelliferyl-beta-D-galactopyranoside and incubation for 20 min at 37 °C. The method was compared with microtiter bioassay (L-YES). P-YES was more sensitive than L-YES and results can be repeated upto one year later.

J. Planar Chromatogr. 35, 189-195 (2022). Planar yeast estrogen screen (pYES) of estriol, daidzein, genistein, 17β-estradiol, 17α-ethinyl estradiol, estrone, 4-nonylphenol and bis(2-ethylhexyl) phthalate on silica gel with cyclohexane - methyl ethyl ketone 2:1 or cyclohexane - cyclopentyl-methyl ether 3:2. Detection under UV light at 272 nm.

Anal. Bioanal. Chem. 413, 1321-1335 (2021). HPTLC of estrone (1), 17β-estradiol
(2), 17α-ethinylestradiol (3), 5α-dihydrotestosterone (4), and progesterone (5) in wastewater and surface water samples on silica gel with a mixture of dichloromethane, cyclohexane, and acetone in different proportions. Detection by spraying with 8 % sulfuric acid in ethanol, followed by heating at 105 ºC for 10 min. Qualitative identification under UV light at 310 nm. Yeast multi endocrine-effect screen was performed by spraying the HPTLC plates with a mixed suspension of genetically modified Arxula adeninivorans yeast strains, which contain either the human estrogen, androgen, or progesterone receptor. The HPTLC plates were incubated at 30 ºC for 18 h and at 100 % humidity. After incubation, densitometric evaluation at: 445/K460 nm, 475/K500 nm and 542/K560 nm to determine the fluorescence of the cyan fluorescent protein (CFP, gestagen), green fluorescent protein (GFP, androgen), and DsRed2 protein (estrogen), respectively. The hRF values for (1) to (5) were 21, 22, 29, 34 and 39, respectively.

J. Liq. Chromatogr. Relat. Technol. 42, 311-316 (2019). HPTLC of equol in cattle manure with methyl t-butyl ether - cyclohexane 1:1. The plate was scanned with a Time of Flight – Direct Analysis in Real Time – Mass Spectrometry (TOF-DART-MS) system. The hRF value of equol was 71. The LOD and LOQ for equol were 2.4 µg/zone and 4.5 µg/zone, respectively. 

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).

J. Planar Chromatogr. 8, 200-204 (1995). Study of the retention behavior of a series of steroids in liquid - solid chromatography as a function of the concentration of the diluent in ternary nonaqueous mobile phases. The relationship between the retention constant RM and the concentration of a diluent in the mobile phase was linear, with the slope values depending on the molecular structures of the compounds.

J. Planar Chromatogr. 31, 72-78 (2018). HPTLC of equol in ethanolic cattle manure extract on RP-18 with n-hexane – ethyl – acetate – acetone 9:3:2. Detection by planar yeast estrogen screening (pYES) by dipping into a yeast suspension, followed by incubation at 30 °C for 4 h. After incubation, the plate was dried in a 37 °C incubator for 15 min and dipped into the combined reaction buffer followed by incubation at 37 °C for 60 min and 90 % relative humidity. The combined reaction buffer was prepared by mixing 20 mL of buffer C (5.3 g of sodium phosphate dibasic and 0.4 g of potassium chloride were dissolved in about 490 mL water, the solution was adjusted with sodium hydroxide to pH 13, 0.5 g of benzalkonium chloride were added and the mixture was filled up to 500 mL) and 0.2 mL of a freshly prepared X-Gal solution (0.05 g/mL X-Gal in DMSO). Fluorescence evaluation under UV 366 nm. The hRF value for equol was 47.

J. Chromatogr. Sci. 34, 330-333 (1996). Two-dimensional TLC on silica with 1) chloroform - acetone 9:1, 2) cyclohexane - ethyl acetate - ethanol 31:8:1 for both directions. Detection by spraying with 95% ethanol concentrated sulfuric acid, heating at 110°C and visualization under UV. Quantification by HPLC.