Spectrophotometric analysis iodide

Maher [130] has described a procedure for the determination of total arsenic in sediments. Arsenic is converted into arsine using a zinc reductor column, as shown in Fig. 12.8. The evolved arsine is trapped in a potassium iodide-iodine solution and other arsenic determined spectrophotometrically as an arsenomolybdenum blue complex. The detection limit is 0.024pg and the coefficient of variation is 5.1% at the 0.1 pg level. The method is free from interferences by other elements at levels normally encountered in sediments. In this method the sediments were freeze-dried and ground (to less than 200pm) before analysis. 

Colorimetric analyzers spectrophotometrically measure the increase in color (absorbance) of a solution resulting from contact with a measured volume of air. The absorbance is linearly proportional to the concentration of the colored species, within known limits. Continuous colorimetric analysis of total oxidants is carried out with a solution of neutral buffered potassium iodide (KI). In 1953, Littman and BenolieF developed the first colorimetric oxidant recorder to come into general use. Instruments of this design, using a 20% neutral buffered potassium iodide solution, later changed to 10%, were incorporated into the Los... 

Placement of the mini-column prior to the sample introduction port can also be useful in unsegmented flow analysis, as demonstrated in the flow injection spectrophotometric determination of molybdenum in plant digests [236]. This method relied on the influence of molybdate anions on the rate of iodide oxidation by hydrogen peroxide under acidic conditions, and some potential interfering cations needed to be separated. To this end, a cation-exchange resin mini-column was attached to the central sliding bar of an injector-commutator hence, it could be displaced between two different streams. Initially, the sample solution was pumped... 

O. F. Kamson, Spectrophotometric Determination of lodate. Iodide and Acids by Flow Injection Analysis. Anal. Chim. Acta, 179 (1986) 475. 

Generally, methods are based on solvent extraction of the additive followed by analysis for the extracted additive by a suitable physical technique such as visible spectrophotometry of the coupled antioxidant, redox spectrophotometric methods, ultraviolet spectroscopy, infrared spectroscopy, gas chromatography, thin-layer chromatography or column chromatography. In general, direct chemical methods of analysis have not foimd favour. These include potentiometric titration with standard sodium isopropoxide in pyridine medium or reaction of the antioxidant with excess standard potassium bromide-potassium bromate (ie. free bromine) and estimation of the unused bromine by addition of potassium iodide and determination of the iodine produced by titration with sodium thiosulphate to the starch end-point. ... 

Spectrophotomelric determination The first spectrophotometric methods proposed for biotin quantification lacked adequate sensitivity and are hardly applied nowadays. The most interesting spectrophotometric method for biotin analysis is based on the reaction of biotin with periodate, resulting in iodate as the reaction product. This iodate reacts with iodide, forming triiodide which is finally measured at 350 to 352 nm. This method has a sensitivity down the microgram level. 

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