J Chromatogr A, 1602, 458–466 (2019). HPTLC of caffeine, physostigmine (alkaloids) and hydroethanolic extract of Peganum harmala seeds (Nitrariaceae, Zygophyllaceae) on silica gel prewashed twice with methanol – water 3:1, followed by 1 h drying at 120 °C. Separation, after 5 min chamber saturation, with ethyl acetate – methanol – ammonia (25%) 85:11:4 (basic mobile phase) or ethyl acetate – toluene – formic acid – water 16:4:3:2 (acidic mobile phase, requiring neutralization with phosphate-citrate buffer). Derivatization with Dragendorff’s reagent and with anisaldehyde sulfuric acid. Effect-directed analysis by spraying A) with Gram-negative bioluminescent Aliivibrio fischeri suspension for antibacterial activity (caffeine was used as standard); B) with acetyl- and butyryl-cholinesterase (AChE / BChE) solutions for enzymatic inhibition. For AChE and BChE asssays, classical immersion into the enzyme solutions was also used for comparison, and inhibition densitometry for active analytes was performed by inverse scan measurement (fluorescence without optical filter) at 546 nm using a mercury lamp; activity was expressed as physostigmine equivalents. Active bands were eluted (only after basic MP) with methanol through the oval elution head of a TLC-MS interface pump, into a quadrupole-Orbitrap mass spectrometer. Full scan mass spectra (m/z 50−750) in positive ionization mode were recorded using heated electrospray ionization (HESI, spray voltage 3.5kV, capillary temperature 270°C). By comparison to literature, AChE inhibitors (also active against A. fischeri) were assigned to be harmine, harmaline and ruine (β-carboline alkaloids), and BChE inhibitors were harmol (same class) and vasicine and deoxyvasicine (quinazoline alkaloids, also called peganine and deoxypeganine). Piezoelectric spraying had the following advantages over automated immersion: (1) it covered the whole plate surface; (2) required much lower volumes of solutions; (3) applied always fresh enzyme or reagent solutions, thus avoiding gradual inactivation; (4) avoided zone distortions, shifts or tailings occurring during immersion or withdrawal of the plate, or due to the hydrophilicity of compounds.

J. Planar Chromatogr. 32, 55-57 (2019). TLC of dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, diisobutyl phthalate, diallyl phthalate, and bis(2-ethylhexyl) phthalate on silica gel with petroleum ether - ethyl acetate - phosphoric acid 9:1:1. Detection by spraying with 0.1 % 2,6-dichlorophenolindophenol with the instantaneous appearance of pink-colored zones.

J. Planar Chromatogr. 24, 113-115 (2011). TLC of dichlorvos on silica gel with cyclohexane - acetone - methanol 16:6:1. Detection by spraying with 2 % sodium hydroxide solution and subsequent spraying with 2 % thiobarbituric solution followed by heating at 90 °C for 10 min. The hRf of dichlorvos was 50. The limit of detection was approximately 18 µg/zone. Spectrophometric analysis of dichlorvos was performed by measuring the absorbance of the sample solution. The linearity was in the range of 50-350 µg/mL dichlorvos. On alkaline hydrolysis dichlorvos forms dimethylphosphoric acid and dichloroacetaldehyde; the latter reacts with 2-thiobarbituric acid to give a sharp pink spot. The reagent is selective for dichlorvos, and does not react with other organophosphorus, organochlorine, carbamate, and synthetic pyrethroid insecticides.

J. Chromatogr. 315, 401-403 (1984). Presentation of a sensitive reagent, sulphosalicylic acid, which is capable of detecting sugars in an amount as low as 0.2 mg on silica thin-layer plates.

J. Planar Chromatogr. 1, 198-213 (1988). Review with 192 references on the analytical uses of fluorodensitometry in HPTLC and on the procedures that may increase sensitivity and selectivity. Illustration of fluorescence enhancement, fluorescence induction and pre- and post chromatographic derivatization methods by application examples.

J. Planar Chromatogr. 3, 500-503 (1990). Descrip-tion of two devices for contact transfer of derivatization reagents using pressure (OPD = “overpressure derivatization”). Influence of the derivatization technique on background noise and linearity was studied. The results obtained tend to prove that OPD is a suitable postchromatographic derivatization method, comparable with spraying and dipping. Densitometric measurements and calibration curves obtained from the method are comparable with those obtained by direct UV detection.

J. Planar Chromatogr. 8, 148-151 (1995). Description of the evaluation of 18 new visualizing agents for the detection of aromatic amines on a) silica, b) a mixture of silica and kieselguhr G with benzene - methanol - acetic acid 45:8:4, and c) polyamide with acetone - ethanol 4:1. For the separation on a) the best visualization results were obtained with bromocresol green, bromothymol blue, sodium hydroxide, thymol blue, and methyl red; for the separation on b) best results were obtained with thymolphthalein. The visualization effects on c) were not as good as on a) and b). The utility of any particular visualizing agent depends on the type of chromatographic support used. The composition and handling of the visualization reagents are given.

J. Planar Chromatogr. 12, 211-214 (1999)., TLC of BrMmC and PAN (4-bromomethyl-7-methoxycoumarin and p-(9-anthroyloxy)-phenacyl bromide) derivatives of carboxylic acids on silica gel and RP silica gel with chloroform - benzene - ethyl acetate 15:3:1, benzene - ethyl acetate 1:1 and 17:1, toluene - ethyl acetate 15:3; hexane - benzene - ethyl acetate 1:3:1, and acetonitrile - tetrahydrofuran 4:1. Fluorodensitometry at 360 nm. Improvement of the results by spraying the plates with a solution of 10% poly(ethylene glycol) 4000 in chloroform. Limit of detection in the lower picomole range.