Trough chambers

Among the verity of PP those containing flavonoids and lipophilic plant ingredients were selected as widely used and rather labile. Sample preparation varied to accommodate certain product type. Samples were chromatographied on Sorbfill HPTLC plates in saturated twin trough chamber. 

In practice a few iodine crystals are usually placed on the bottom of a dry, closed trough chamber. After the chamber has become saturated with violet iodine vapor the solvent-free plates are placed in the chamber for 30 s to a few minutes. The iodine vapor condenses on the TLC layers and is enriched in the chromatogram zones. Iodine vapor is a universal detector, there are examples of its application for all types of substances, e.g. amino acids, indoles, alkaloids, steroids, psychoactive substances, lipids (a tabular compilation would be too voluminous to include in this section). 

Acetanilide, p-chloro-acetanilide, 2,5-dichloro-acetanilide Apply sample solution and treat with chlorine vapor in the trough chamber for 20 s, then heat to 60°Cfor 5 min in a ventilated drying cupboard. Various chlorination patterns are produced. [44]... 

Polycyclic aromatic hydrocarbons (PAH) Apply sample solution and dry. Place TLX2 plate for 20 min in a twin-trough chamber containing phosphorus pentoxide to which 2 to 3 ml cone, nitric acid have been added. PAH nitrated by nitrous fumes. [20]... 

Fig. 43 Twin-trough chambers (A) and conditioning chamber (B) (Camag).

Apart from such trough chambers there are also S-chamber systems (small chambers, sandwich chambers) with deliberately reduced vapor volumes, which are specially suited to adsorptive separations. Such chambers are available for vertical and horizontal development (Fig. 58). Different separation results are naturally obtained in trough and S-chambers [8]. 

The twin-trough chamber (Fig. 43A) was not just developed to economize in mobile phase it also allows the layer to be impregnated as desired from the vapor... 

One-dimensional, ascending development in a trough chamber with chamber saturation. 

The chromatograms are dried in a stream of cold air (alkaloids 110 —120°C for 25 min in drying cupboard) and placed for 15 min in a twin-trough chamber — in the case of alkaloids while still hot — whose second trough contains 10 ml 25% ammonia solution. 

Ascending, one-dimensional development in a trough chamber without chamber saturation. 

Detection and result The chromatogram was heated in the drying cupboard to 110 —120°C for 25 min and immediately placed — while still hot - in a twin-trough chamber, whose second trough contained 10 ml 25% ammonia solution, for 15 min. The chromatogram was then immersed for 2 s in a solution of liquid paraffin — n-hexane (1 + 2). 

A) Ascending, one-dimensional, double development in a trough chamber (5 min drying in warm air between developments) with chamber saturation. 

Note Note that the diazotization of primary aromatic amines can also be achieved by placing the chromatogram for 3 — 5 min in a twin-trough chamber containing nitrous fumes (fume cupboard ). The fumes are produced in the empty trough of the chamber by addition of 25% hydrochloric acid to a 20% sodium nitrite solution [2, 4], iV-(l-Naphthyl)ethylenediamine can be replaced in the reagent by a- or -naphthol [10, 14], but this reduces the sensitivity of detection [2]. Spray solutions Ila and lib can also be used as dipping solutions. 

Detection and result The chromatogram was freed from mobile phase (10 min in a stream of warm air) and placed for 10 min in the empty half of a twin-trough chamber in whose second half nitrous fumes were being generated by the addition of 10 drops 37% hydrochloric acid to 5 ml 20% aqueous sodium nitrite solution. After the nitrous fumes had cleared (3 —5 min in air, fume cupboard ) the chromatogram was immersed in solution Ila for 1 s and dried in a stream of cold air. 

Ascending, one-dimensional development in a twin-trough chamber with chamber saturation with the layer being preconditioned in the solvent-free half of the trough for 15 min after application of the sample. 

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. 

Detection and result The chromatogram was freed from mobile phase in a stream of warm air, then immersed in dipping solution I for 1 s, dried for 90 s in a stream of warm air and after cooUng immersed in dipping solution II for 1 s. After drying briefly in a stream of warm air it was heated to 110°C for 2 min and treated with hydrochloric acid vapor for 15 min in a twin-trough chamber (37% hydrochloric acid in the vacant trough). 

The chromatograms stained with ninhydrin are immersed in the reagent solution for 1 s or sprayed evenly with it and then placed in the free half of a twin-trough chamber containing 25% ammonia solution. Apart from proline and hydroxyproline, which yield yellow copper complexes, all the amino acids yield reddish-colored chromatogram zones [3],... 

Note If the spray solution or a nonbasic dipping solution [2] is employed for detection then it is advisable to spray again with a 10% aqueous sodimn carbonate solution. The necessary basicity can also often be achieved by placing the treated chromatogram in a twin-trough chamber whose second trough contains 5 ml ammonia solution (25%). 

Ascending, one-dimensional development in a trough chamber. After sample application the HPTLC plates were equilibrated in a conditioning chamber at 42% relative humidity for 30 min and then developed immediately. 

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