Anal. Bioanal. Chem. 411, 6213-6225 (2019). HPTLC of selected analgesics (acetaminophen), alkaloids (nicotine and caffeine), and steroids (cortisone) on different
stationary phases (silica gel, RP-, cyano-, DIOL- and amino-) with isopropyl alcohol - n-heptane - water 7:3:1. Direct surface analysis of the TLC plates with a flowing atmospheric pressure afterglow (FAPA) ambient desorption/ionization source (TLC-FAPA-MS). The LOD of caffeine was 0.6 ng/zone. Semi-polar stationary phases (cyano and RP plates) showed significantly higher signal abundances for the analyzed compounds in comparison to the polar NP stationary phase.

Anal. Bioanal. Chem. 412, 4527-4536 (2020). HPTLC of 20 chemicals representative of migrants from plastic food contact materials on silica gel with chloroform - acetone - petroleum ether 11:5:5. Yeast estrogen screen was performed by spraying with yeast culture, followed by incubation at 30 ºC for 3 h. Detection by spraying with the indicator (2 mL 0.5 mg/mL 4-methylumbelliferyl-β-D-galactopyranoside-MUG in lacZ buffer), followed by incubation at 37 ºC for 20 min. Qualitative identification under UV light at 366 and 550 nm. The method was more sensitive than a microtiter plate YES (lyticase-YES). 

Anal. Bioanal. Chem. 411, 6767-6775 (2019). HPTLC of nonylphenols in surface waters on RP-18 with n-hexane - acetonitrile - toluene 8:4:3, followed by a second development with n-hexane - ethyl acetate - toluene 5:8:1. Yeast estrogen screen was performed by dipping into a suspension of genetically modified Saccharomyces cerevisiae BJ3505 cells, followed by incubation at 30 ºC for 4 h with a relative humidity of approximately 100 %. The dried plate was then immersed in the substrate solution for 3 s (0.1 mg/mL resorufin-β-D-galactopyranoside - RGP) and again incubated at 37 ºC for 30 min. Drying, dipping, and incubation with RGP was repeated two times. Quantitative determination by fluorescence measurement at 550 nm/> 580 nm. Linearity was between 15 and 40 ng/zone. The LOD and LOQ were 14 and 26 ng/zone. Average recovery was 95 %.

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.

Anal. Bioanal. Chem. 412, 7441-7451 (2020). HPTLC of mono- (1) and diacylglycerol (2) emulsifiers (E 471) in whipping creams on primuline impregnated silica gel with n-pentane - n-hexane - diethyl ether 9:9:22. Quantitative determination by fluorescence measurement at UV 366/> 400 nm. The hRF values for (1) and (2) were 10 and 52, respectively. Linearity was between 1.5 and 20 ng/zone for (1) and (2). Intermediate precision was below 7 % (n=4). The LOD and LOQ were 1.8 and 5.7 ng for (1) and (2). Recovery was between 95 and 105 % for (1) and 86 and 95 % for (2).

Anal. Bioanal. Chem. 412, 2633-2644 (2020). HPTLC of  cannabinol in sediment samples on silica gel with n-heptane - diethyl ether 9:1. Detection by spraying with cerium- molybdenum reagent (400 mg cerium IV sulfate and 20 g ammonium molybdate in 400 mL 10 % sulfuric acid). HPTLC plates were further analyzed by electrospray ionization mass spectrometry. The hRF value for cannabinol was 20. Linearity was between 25 and 155 ng/zone. Intermediate precision was below 5 % (n=3). The LOD and LOQ were 6 and 21 ng/zone. Average recovery was 73 %.

Anal. Bioanal. Chem. 411, 725-734 (2019). HPTLC of bisphenol A (1) and its nine brominated analogs, namely monobromobisphenol A (2), 2,2’-dibromobisphenol A (3), tribromobisphenol A (4), tetrabromobisphenol A (TBBPA) (5), TBBPA mono(methyl ether) (6), TBBPA mono(allyl ether) (7), TBBPA mono(2,3-dibromopropylether) (8), TBBPA bis(allyl ether) (9), TBBPA bis(2,3-dibromopropyl ether) (10) in chicken samples on silica gel with n-hexane - ethyl acetate - dichloromethane - acetic acid 25:5:5:1. Detection at UV 254 nm. Further analysis by high-performance liquid chromatography-diode array detector/triple quadrupole mass spectrometry. The hRF values for (1) to (10) were 30, 32, 33, 45, 58, 68, 69, 69, 91 and 86, respectively.  

Anal. Bioanal. Chem. 412, 2237-2249 (2020). HPTLC of sphingomyelin (1), phosphatidylcholine (2), and triacylglycerol (3) fractions from preadipocytes and adipocytes on silica gel with chloroform - ethanol - water - triethylamine 30:35:7:35 for (1) and (2) and hexane - diethyl ether - acetic acid 80:20:1 for (3). Detection by dipping into primuline (dissolved in acetone - water 4:1) and under UV light at 366 nm. Lipid fractions were further analyzed by electrospray ionization-ion trap mass spectrometry.