Staining methods iodine method

One good method of detection on TLC plates is the use of iodine. After the plate has been run and dried, it is placed in a closed container containing iodine. The iodine vapor reacts with double bonds in the compounds to form brown complexes. If iodine doesn t work, then other staining methods will have to be examined6 (ideally the staining method should be reversible so that the compound identity can be confirmed by HPLC after the plate has been run and stained). 

TEM or SEM examination of inclusion compound...The blue stained (alginate-iodine compound) film sample and the red stained(alginate-Food color Red No.105 compound) bead sample were stained negatively with 57o uranyl acetate, made by the usual method and observed by 200kV TEM (Hitachi H-800). The shrunk and hard bead separated from acetic acid (alginate-cholesterol adduct) sample was prepared in the same manner described above(for SEM sample) and observed by SEM(Hitachi S-430). 

The authors are grateful to Prof. Amanda Murphy for suggesting this method. It is best to prepare the jar at least one day in advance of class period to allow the iodine to disperse evenly throughout the silica gel. The silica gel should be evenly stained with iodine. When the mixture is first prepared, the silica gel will appear pink, but it will turn to a rusty orange color over time. 

There are few current applications of the iodine staining or sorption method found in the literature. Even in early studies, the destaining of polymers at room temperature and the volatilization in the vacuum of the electron microscope showed limitations of the method. Overall, there appears to be simple physical adsorption of the iodine, preferentially in the amorphous regions of semicrystalline polymers. 

Figure 1. Action pattern of Bacillus circulans F-2 amylase. Culture supernatant was applied to PAGE and stained for amylase activity with starch—iodine method. Action patterns of groups I and II toward soluble starch were studied thin-layer chromatography. (Reproduced with permission from ref. 7. Cbpyright 1989 Elsevier.)...

Size polymers on polyester can be determined by staining tests with Cl Basic Red 22, Cl Reactive Red 12, iodine/potassium iodide solution, or a mixed indicator. The extraction of size components and their determination in solution using a variety of reagents to give a characteristic coloration or a coloured precipitate has been described. Methods using fluorescence spectroscopy with a fluorescent cationic dye (e.g. Pinacryptol Yellow or Cl Basic Orange 14) were also described. 

After a plate has been exposed to the mobile-phase solvent for the required time, the compounds present can be viewed by several methods. Polynuclear aromatic hydrocarbons, other compounds with conjugated systems, and compounds containing heteroatoms (nitrogen, oxygen, or sulfur) can be viewed with long-and short-wave ultraviolet light. The unaided eye can see other material, or the plates can be developed in iodine. Iodine has an affinity for most petroleum compounds, including the saturated hydrocarbons, and stains the compounds a reddish-brown color. 

Indinavir sulfate may be analyzed by TLC using E. Merck silica gel 60F-254 high performance thin layer chromatographic plates, and eluted with a mobile phase of 8 1 1 (v/v/v) ethyl acetate methanol ammonium hydroxide [8], Visualization was performed by developing the plate with iodine stain, and viewing under short-wave UV (254 nm) light. When using this method, the Rf of indinavir sulfate is approximately 0.6 [8]. 

Gram s Method.—This is a method of differential bleaching after a stain. The cover glass preparations or sections are passed from absolute alcohol into Ehrlich s anilin gentian violet, where they remain one to three minutes, except tubercle bacilli preparations which reniain commonly twelve to twenty-four hours. They are then placed for one to three minutes (occasionally five minutes) in iodine potassium iodide water (iodine crystals i, potass, iodide 2, water 300), with or without washing lightly in alcohol. In this they remain one to three minutes. They are then placed in absolute alcohol until sufficiently bleached, after which they are cleared in clove oil and mounted in balsam. 

Gram (Gram s Stain) A method for separating bacteria whereby bacteria are stained first with crystal violet (a red dye) and then washed with an iodine solution. Gram positive bacteria (Bacillus) retain the dye. Gram negative bacteria (Pseudomonas and some Bacillus) lose the dye. 

The facility of the enzymic methods is evidenced by the large number of publications coming from laboratories specializing in routine analytical studies on polysaccharides of this type, as well as from oim own work ( see, for example. Ref. 287). Although enzymic methods, by themselves, are generally completely definitive, additional evidence, such as that from iodine-staining measurements, may in some instances be useful. ... 

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