Reagent iodine vapor

Iodine starch inclusion compounds 46 Iodine vapor reagent 46, 64, 78 2-Iodoestrone 66 Ipecacuanha alkaloids 46, 263 Ipecacuanhae radix extract 263 Iron cadons 144, 217, 311 Iron(IIl) chloride reagent 170,216,314 Iron(III) thiocyanate reagent 170 Isoascorbic acid 376 Isoleucine 246,247... 

Most of the thiazoles studied absorb in the ultraviolet above 254 nm, and the best detection for these compounds is an ultraviolet lamp (with plates containing a fluorescent indicator). Other indicator systems also exist, among which 5% phosphomolybdic acid in ethanol, diazotized sulfanilic acid or Pauly s reagent (Dragendorff s reagent for arylthiazoles), sulfuric anisaldehyde, and vanillin sulfuric acid followed by Dragendorff s reagent develop alkylthiazoles. Iodine vapor is also a useful wide-spectrum indicator. 

Fig. 36 Dependence of the area of the chromatogram zone at constant amount of applied substance (1 pg) on the reagent employed, top relief representation, below zone areas projected on one another Iodine vapor reacts least sensitively here, aniline-phthalate most sensitively and the GOD reaction (glucose oxidase reaction) most specifically [2161...

Note The TDM reagent can be used everywhere, where o-tolidine is employed. It can also be used on chromatograms, that have already been treated with ninhydrin, Pauly or ammonia perchlorate reagent or with iodine vapor [1]. Water may be used in place of 80% 2-propanol when making up solutions II, III and IV. The chlorine gas atmosphere in the chromatography chamber can also be created by pouring 5 ml hydrochloric acid (ca. 20%) onto 0.5 g potassium permanganate in a beaker such a chlorine chamber is ready for use after 2 min. 

Note It is occasionally recommended that sodium acetate be added to the reagent [2]. Thiophosphate insecticides with a simple P—S bond yield yellow chromatogram zones and those with a P=S double bond yield brown ones on a light brown background [10]. Further treatment of the stained chromatogram with iodine vapors increases the detection sensitivity [7] more than does spraying afterwards with caustic soda solution, which is also occasionally recommended [16, 17, 20, 21]. 

A versatile detection reagent for lipids is iodine vapor. The dry plate is placed into a chamber containing one or two Petri dishes with crystals of solid iodine. Lipid-containing spots are colored yellow to brownish after few minutes. The color disappears quickly in contact with air. 

The ninhydrin test will not interfere with the Ehrlich reagent. Therefore, a plate can be examined under UV light, immersed in iodine vapors, treated with ninhydrin, and the Pauly or Ehrlich reagents successively. 

Several hundred reagents are described as being useful for substance visualization [6,27,52,53]. A relatively common test is to place the sorbent into a tank of iodine crystals. The iodine vapors form weak-charge transfer complexes with unsaturated bonds of the sample. This is visibly detected as brown spots. Reaction with iodine is generally reversible but has been shown to oxidize compounds such as mercaptans and disulfides. 

Silica gel 60G-coated plates can be used with thin-layer chromatography, and a suitable solvent system is butanol-acetic-water (6 2 2, v/v). If the product is pure sphingosine-l-P, it should migrate with an Rf value of 0.48. It will give a positive reaction to the phosphorus and ninhydrin reagents, as well as exhibiting a positive reaction to iodine vapors. 

Cephalosporines are derived from natural cephalosporin C produced by Cephalosporinum acre-monium. They possess a cephem nucleus (7-amino-cephalosporanic acid) substituted with two side chains. They are commonly divided into three classes differing in their spectra and toxicity. Cephalosporines can be analyzed both by normal and reversed-phase TLC or HPTLC hence, more efficient separation is obtained on sUanized gel than on bare, untreated silica gel. Mobile phases are polar and similar to those used for penicillins. Acetic add or acetates are very often components of solvents for normal phase (NP) TLC, the ammonium acetate-acetic acid buffer for RP TLC. All cephalosporines can be detected at 254 nm. The detection limit can be diminished by applying reagents such as ninhydrin, iodoplatinate, chloroplatinic acid, or iodine vapor. Alternative to UV detection is bioautography with, for instance. Neisseria catarrhalis. 

Other nondestructive detection methods use iodine vapors or iodine-potassium iodide reagents (Mylius s reaction). Yellow, orange, or brown zones will appear on the layer. The zones will have to be marked, because the iodine will eventually evaporate. The sensitivity of the iodine test can be greatly increased by the use of layers containing rhodamine 6G. Most of the steroids are recovered unchanged af-... 

---