Iodine-containing compounds detection

Walash et al. [14] described a kinetic spectrophotometric method for determination of several sulfur containing compounds including penicillamine. The method is based on the catalytic effect on the reaction between sodium azide and iodine in aqueous solution, and entails measuring the decrease in the absorbance of iodine at 348 nm by a fixed time method. Regression analysis of the Beer s law plot showed a linear graph over the range of 0.01 0.1 pg/mL for penicillamine with a detection limit of 0.0094 pg/mL. 

Spot Mercaptans and thioketones markedly catalyze the reaction of sodium azide with iodine with liberation of nitrogen, and this catalyst is used for detection of the sulfur containing compounds. 

Following inhalation exposure, the primary route of excretion of unmetabolized carbon disulfide in humans is exhalation. In one study it was estimated that 6-10% of the carbon disulfide that was taken up was excreted by the lungs (McKee et al. 1943). In a study conducted on humans, carbon disulfide levels in the exhaled breath decreased rapidly on cessation of exposure (Soucek 1957). The excretion by the lung accounted for 10-30% of the absorbed carbon disulfide. Less than 1% was excreted unchanged in the urine. The remaining 70-90% of the dose was metabolized. The details regarding carbon disulfide exposure levels were not available. A correlation was established between carbon disulfide exposure of rayon workers and urinary excretion of a metabolite or metabolites that catalyzed the reaction of iodine with sodium azide (Djuric 1967). This test indicated exposures to carbon disulfide above 16 ppm but failed to identify specific urinary metabolites. The failure to detect carbon disulfide exposure below 16 ppm may be because of interference with the reaction by dietary sulfur-containing compounds. 

A. Iodine The universal detection reagent iodine is used either as a 1% alcoholic spray, or the plate is placed in a closed jar or tank containing iodine crystals. The iodine vapor dissolves in, or forms weak charge-transfer complexes with organic compounds, which show up as brown spots on a pale yellow background within a few minutes. After marking zones for future reference, exposure of the plate to air causes the iodine to sublimate and the spots to fade, after which the plate can be sprayed with another reagent or the solute can be eluted from the plate for further analysis. 

The free iodine can be detected by the starch test. When applying the redox reaction with iodide, it should be remembered that antimony-bearing organic compounds leave antimony pentoxide or calcium antimonate after ignition with lime and these compounds also set iodine free. The same is true when the ignition residue contains ferric oxide. 

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. 

Iodine interacts with many organic compounds to form pi complexes that are colored. This method of detection is especially useful for lipids containing double bonds. A lipid with several double bonds will give a darker spot with iodine. The darker spots may also be due to a higher concentration of lipid. 

A useful general, but unspecific, detecting agent for most organic compounds is iodine vapour. The dried plate is allowed to stand in a closed tank containing a good supply of iodine crystals scattered over the tank bottom usually the spots are revealed as brown stains. Their positions should be marked as soon as the plate has been removed from the iodine tank since standing in air for a short while causes the iodine to evaporate and the stains to disappear. 

Iodine and Se speciation in breast milk provides an example of the use of CE in hyphenated systems with ICP-MS detection. By employing CE, Michalke and colleagues determined selenoaminocids and identified two chemical forms of iodine, I- and thyroxine, which were present in comparable amounts in milk [115-117]. Other authors used SEC and IEC for I speciation in various types of milk and infant formulae (see Table 8.3) and found I- as the main species, with the exception of breast milk and formulae. The latter were found to contain less I than commercial and human milk, and mostly as an unidentified macromolecular compound. 

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