Dipping in reagent solutions

The dried chromatogram is first dipped in reagent solution 1 for 1 s, dried briefly in a stream of cold air and then dipped in reagent solution 2 for 1 s. The TLC/HPTLC plate is then held upright on tissue paper to allow excess reagent to drain away when the layer appears matt it is covered with a glass plate and kept at room temperature for 5 min. Afterwards it is dried in a stream of hot air and exposed to ammonia vapor. 

Estrone, estradiol, estnol Dip silica gel foil 2 cm in saturated Fast Black Salt K. solution and dry in a stream of warm air. Apply sample solution, dip again in reagent solution and dry. Dip the TCL plate 2 cm in 4% pyridine-cyclohexane solution, dry at 100 to 200°C and develop the azo-dyestuffs that are formed. [294]... 

Detection and result The chromatogram was dried in a current of warm air and either immersed in reagent solution I for 1 s or placed for 15 min in a twin-trough chamber in whose second trough 5 ml of dipping solution I had been placed ca. 10 min previously. If the chromatogram was derivatized by dipping it had to be dried for ca. 1 min in a stream of hot air and allowed to cool to room temperature. 

Note The reagent can be employed on silica gel, kieselguhr. Si 50 000 and RP layers [6]. The fluorescence intensities of the chromatogram zones can be increased by dipping in a solution of liquid paraffin in hexane or chloroform [8,11]. 

If the reaction proves difficult the TLC plate should first be dipped in 1 % solution of triethylamine in acetone or in a solution of 1 to 2 drops sodium hydroxid solution (c = 10 mol/1) in methanol to optimize the pH for the reaction. This effect can also be achieved by employing borate buffer, pH = 11, instead of acetone in the spray reagent [10,11]. 

After the chromatograms have been freed from mobile phase in a stream of warm air for 3 min they are inunersed in dipping solution 1 for 3 s or homogeneously sprayed with it and then dried in a stream of warm air. Then they are dipped in reagent solu-... 

Many studies have been recently focused on impregnated plates. The methods used for impregnation depend on whether the plates are home-made or commercially available. In the first case, the impregnation reagent is usually added to a slurry of the adsorbent, whereas ready-to-use plates are dipped in the solution of the reagent. 

Lead tetraacetate-2,7-dichlorofluorescein (A) lead tetraacetate (saturated solution) in glacial acetic acid (B) 2,7-dichlorofluorescein in water (1%, m/v, or lower, down to 0.2%, if background interferes with detection) A and B are mixed 1 1 (v/v), then toluene (19 1, v/v) is added Plate is dipped in reagent for 10s, then heated at 100°C for 3 min All carbohydrates with vicinal diol groups, oxidized by lead tetraacetate, are detected fluorimetric scanning (excitation 313nm, emission 366 nm) 50-100pmol... 

The chromatogram is freed from solvent, dipped in the reagent solution for 5 — 10 s and then heated to 120—150°C for 5 — 10 min. (Caution Remove perchloric acid from the back of the chromatographic plate ). 

Detection and result The chromatogram was dried in a stream of warm air for 1 min, after cooling it was immersed for 1 s in the reagent solution. After redrying in a stream of warm air it was dipped into a mixture of chloroform — liquid... 

The chromatogram is freed from mobile phase, dipped for 1 s in the reagent solution or sprayed evenly with it until the plate begins to be transparent and dried in a stream of cold air. 

Detection and result The chromatogram was dried in a stream of cold air and then intensively irradiated with UV Ught (A = 365 nm) for 2 min and then immersed in the reagent solution for 1 s. It was finally heated to 120°C for 10 min and after cooling dipped into hquid paraflln — n-hexane (1 2) to intensify and stabilize... 

The phenols pyrocatechol, resorcinol and hydroquinone can be detected with all chloramine T reagents. The detection sensitivity is about the same with chloramine T - sodium hydroxide and chloramine T - trichloroacetic acid. In all cases the detection limits are ca. 75 ng substance per chromatogram zone after the plate has been subsequently dipped in a paraffin oil solution. Somewhat less favorable detection limits of 150 to 200 ng substance per chromatogram zone are obtained after treatment with chloramine T - hydrochloric acid and chloramine T - sulfuric acid. 

In situ quantitation The fading of the fluorescence on exposure to heat and on allowing the chromatograms to stand makes this reagent unsuitable for in situ quantitation. Dipping the chromatograms in paraffin solution does not improve this (Fig. 2). 

The dried chromatograms are dipped in the reagent solution for 3 s or sprayed homogeneously with it and then heated to 105 °C for 5 min. After cooling to room temperature the chromatograms are then immersed in the dipping solution or homogeneously sprayed with the spray solution. They are finally dried at 90 °C for 5 min [1, 2]. 

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