Staining iodine

Some substances, e. g. penicillin and pyrazolinone derivatives, are poorly detected by iodine staining with detection limits of 2-4 pg substance per chromatogram zone [6, 7]. The limits for lipids and for opium alkaloids lie with 50-500 ng [8] in the middle nanogram range [9]. 

In addition to the iodine staining resulting from adsorption or purely physical solution of the iodine molecules in the lipophilic chromatogram zones, many substances can also be made visible by chemical reaction with the iodine [9]. In such... 

Insulin derivatives lb 401 lodate anions la 188,190 lb 307 Iodine staining lb 278 Iodine-azide reaction lb 85,301-304 Iodide anions la 190 lb 76,77,128,129 Iodide vapor la 46,64,78 lodination la 66... 

The linear arrangement of iodine atoms in the amylose inclusion compound has generated much interest right from the early days with respect to its spectroscopic and optical properties 138 -140). It has also been known for many years that polyvinyl alcohol (PVA) behaves similarly, and this was applied by Polaroid Corporation for the manufacture of polarising plastic using stretched sheets of iodine-stained polyvinyl alcohol170). 

From measurements of the dichroism of flow of amylose-iodine solutions,161 and from studies of the optical properties of crystalline amylose platelets and iodine-stained platelets,163 it was shown, following the suggestion of Hanes, that a helical configuration of the amylose in this complex is probable. This was later confirmed by x-ray measurements (see p. 378) the iodine atoms were shown to be situated in the core of helically-oriented amylose molecules. 

If the mixture components are not colored, any of a number of techniques designed to make the spots visible may be employed. These include iodine staining, in which iodine vapor is allowed to contact the plate. Iodine will absorb on most spots, rendering them visible. Alternatively, a fluorescent substance may be added to the stationary phase prior to the separation (available with commercially prepared plates), such that the spots, viewed under an ultraviolet light, will be visible because they do not fluoresce while the stationary phase surrounding the spots does. 

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]. 

Other agents are also available, which are used to remove pigmentation of teeth e.g. weak ammonia solution is used to remove iodine stains, hypochlorite or iodine solution are used to remove silver stains, hypochlorites are used to remove iron stains of teeth and for dye stains, chlorinated lime and acetic acid are used. 

Sauer and Fitzgerald [9] have described thin layer chromatographic technique for the identification of water-borne petroleum oils. Aromatic and polar compounds are removed from the sample by liquid-liquid extraction with acidified methanol, the extract is chromatographed on a silica gel thin layer plate, and the separated components are detected by their fluorescence under long- and short-wave ultraviolet light. Unsaturated non-fluorescing compounds are detected by iodine staining. 

Uses For bleaching bromide prints in sulfide toning with potassium cyanide as a print reducer for removing silver stains. Iodine stains on fingers disappear in hypo or sulfite. 

Starch from ae su kernels in a dent background consists of 51-60% amylose, as determined by the blue value procedure (Table 3.6), with the amylose percentage increasing with increasing kernel age.57 Yeh et al.,90 in contrast, reported that ae su reduced amylose concentration from 65% for su to 28% for ae su, based on SEC separation of starch polysaccharides isolated from kernels in a sweet com background. Three fractions were obtained (Table 3.7). The first two were loosely-branched, similar to the amylopectin fractions in ae. Amylose from the third peak fraction was similar in iodine staining to that from normal however, some short chain length amylose as... 

Branching linkage assay (b) Iodine stain assay (c) 2.6 0.32 0.14... 

Figure 9.1 Longitudinal 10-pm bisection ofa steeped dent com kernel (magnified X6, iodine stained). Note how starch has been lost from floury endosperm cells as a result of sulfur dioxide action.

Figure 9.2 Section of steeped corn horny endosperm (1 Op,m thick, iodine stained, magnified X612 SG, starch granules PM, protein matrix CW, cell wall).

Figure 9.3 Longitudinal 10-pm bisection of a steeped grain sorghum kernel (magnified X22, iodine stained).

Record the distance the solvent front advanced on your Report Sheet (4). Record on your Report Sheet (5-9) the distance of each iodine-stained spot from its origin. Calculate the Rf values of your samples (10-14). 

Bailey, J. M., and Whelan, W. J. 1961. Physical properties of starch. 1. Relationship between iodine stain and chain length. J. Biol. Chem. 236, 969-973. 

Fales, F. W. 1980. The linear relationship between iodine staining and average chain length of the unbranched amyloglucans. Biopolymers 19, 1535-1542. 

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