Dipping reagents

In general care should be taken in the choice of solvent to ensure that neither the chromatographically separated substances nor their reaction products are soluble in the solvent of the dipping reagent. 

Note The dipping reagent, which can also be applied as a spray reagent, can be employed on cellulose and silica gel layers. A 3% solution of 2,2 -bipyridine in 40% thioglycolic acid can be employed as a specific spray reagent for the detection of iron (red coloration) [7],... 

Detection and result The chromatogram was freed from mobile phase in the drying cupboard (5 min 100 "C), immersed in the freshly prepared dipping reagent for 1 s and then heated to 100"C for 10 min. 

The chromatograms are dried in a stream of warm air, then placed for 10—15 min in the empty half of a twin-trough chamber whose other trough contains 25 ml cone, ammonia solution (equilibrate for 60 min ) and then immediately immersed in the dipping reagent for 5 s [18] and dried for 5 min in a stream of warm air. 

Note The dipping reagent is to be preferred because of the strongly irritating effects of formaldehyde on the respiratory tract. Detection limits of ca. 10—40 ng have been reported for alkaloids [4] and 50 ng — 1 pg for -blockers [2, 3]. 

The dipping reagent may be stored in the refrigerator for several weeks. 

The dipping reagent can be used, for example, on silica gel, kieselguhr. Si 50000, RP 18, NH2, Diol and CN layers. It is not possible to detect aromatic amines on cellulose layers [1]. 

Dipping chambers la 83 Dipping reagents la 82ff -, choice of solvent la 85 Dipropropretryn lb 207,208,230, 231, 413,414... 

Wherever possible, dipping reagents have been employed instead of the spray reagents that were formerly commonplace. These make it easier to avoid contami-... 

For the separation of aminoglycoside antibiotics with a linear chamber on silica gel HPTLC plates (Merck), the solvent methanol/25% ammonia (2 3) was used (31). The dipping reagent was 0.3 g of ninhydrin + 100 ml of 1-butanol + 3 ml of acetic acid. The / y values were... 

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