Spray reagents

Hydantoin itself can be detected ia small concentrations ia the presence of other NH-containing compounds by paper chromatography followed by detection with a mercury acetate—diphenylcarba2one spray reagent. A variety of analytical reactions has been developed for 5,5-disubstituted hydantoias, due to their medicinal iaterest. These reactions are best exemplified by reference to the assays used for 5,5-diphenylhydantoiQ (73—78), most of which are based on their cycHc ureide stmcture. Identity tests iaclude the foUowiag (/) the Zwikker reaction, consisting of the formation of a colored complex on treatment with cobalt(II) salts ia the presence of an amine (2) formation of colored copper complexes and (3) precipitation on addition of silver(I) species, due to formation of iasoluble salts at N. ... 

Note The dipping solution can also be employed as spray reagent. The detection limits per chromatogram zone are reported to be 1 — 5 pg substance [1] for the oxyacids of halogens and ca. 10 pg substance for reducing sugars [4]. 

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],... 

The dipping solution can also be employed as spray reagent, in this event 60% [6], 80% [5] or 95% ethanol [9] have been recommended in the literature. The reagent can be employed on silica gel, Dowex 50X4 (Na ), cellulose and starch layers. The detection limit for 1,4-benzodiazapines is 100 ng per chromatogram zone [11]. 

The chromatograms are dried in a stream of warm air or at 105 °C for 10 min, cooled to room temperature and sprayed homogeneously with the spray reagent until they start to become transparent. 

Variant I The chromatogram is dried in a stream of warm air or in the drying cupboard (10 min, 120 °C), cooled to room temperature and either sprayed with spray solutions la and lb one after the other (with brief drying in a stream of cold air in between) [1] or sprayed with a mixture of equal volumes of these two spray reagents until the layer begins to be transparent [2, 4]. 

Detection and result The chromatogram was dried in a stream of cold air fo 2 min and sprayed three times with the spray reagent until it began to appeal transparent. The plate was dried in cold air after each spray step and finally heater to 120°C for 15 min. Lecithin hRf 15) and sphingomyelin hR( 5 — 10) appearet as dark blue zones on a yellow background (Fig. 1). 

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]. 

Note The dipping solution can also be employed as a spray reagent. 

Note Rhodamine 6G is a universal reagent which can also be incorporated in the TLC layers [4, 9] or added to the mobile phase [4], The spray reagent can also be made up in water [8], acetone [4, 6] or ammonia solution (c = 2.5 mol/1) [5]. The visual detection limit is most favorable when the water from the mobile phase or the detection reagent has not completely evaporated from the layer. This can be recognized by the fact that the background fluorescence has not turned from red to pink [4]. 

For sulfoxides The dried chromatograms are sprayed homogeneously with spray reagent III. After a few minutes they can then be sprayed with spray solution IB to increase the color contrast [8, 9]. 

Patil VB, Sevaikar MT, Padalikar SV. 1987. Specific spray reagent for the detection of endosulfan by thin-layer chromatography. J Chromatogr 396 441-443. 

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

Firstly, the dried chromatograms are homogeneously sprayed sequentially with s] solutions I and 2 and then, after being allowed to stand for 5 min, they are sprayed reagent 3. 

The Dragendorjf reagent is available in different compositions, and it mainly stains nitrogen-containing compounds, producing colored zones on a white background. For solntion a 1.7 g of basic bismuth nitrate and 20 g of tartaric acid are dissolved in 80 ml of water. For solution b 16 g of potassium iodide are dissolved in 40 ml of water. The final spray reagent is mixed from solution a and b in the... 

Chapter 7 describes nondestructive (reversible) detection of snbstances by using iodine or water. Iodine can detect a wide variety of chemical classes as brown to yellow-brown zones on a preparative layer after exposnre to its vapor or dipping into a 1% iodine in chloroform solution. Another general, nondestmctive technique for detection of hydrophobic compounds in PLC nses water as a spray reagent [12-14]. 

This material, normally supplied or stored in sealed ampoules and used as a paper chromatography spray reagent, is photo-sensitive. Exposure to UV light causes exothermic decomposition to acetone and chloromethane. Ampoules have burst because of pressure build-up after exposure to fluorescent or direct day light. Store cool and dark, and open ampoules with personal protection. The material also reacts violently with rubber [1,2], It should not be heated to above its boiling point [3], There is also a preparative hazard. 

Color Reactions of 4(5)-Aminoimidazole (25 R = H) with Spray Reagents... 

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