Iodine, detection recovery

Iodine, detection of, 1041, 1042, 1043, 1045 recovery of, 647 Iodine monochloride, 974 5-Iodo-2-ammotoluene, 647 p-Iodoaniline, 647 Iodobenzene, 533, 538, 591, 598 Iodobenzene diacetate, 541 Iodobenzene dichloride, 534, 541 o-Iodobenzoic acid, 760... 

Puacz et al. (1995) developed a catalytic method, based on the iodine-azide reaction, for the determination of hydrogen sulfide in human whole blood. The method involves the generation of hydrogen sulfide in an evolution-absorption apparatus. In addition, the method allows for the determination of sulfide in blood without interference from other sulfur compounds in blood. A detection limit of 4 g/dm3 and a percent recovery of 98-102% were achieved. Although the accuracy and precision of the catalytic method are comparable to those of the ion-selective electrode method, the catalytic method is simpler, faster, and would be advantageous in serial analysis. 

Another method developed for the determination of iodide was GC—mass spectrometry (Mishra et al., 2000). Iodide was oxidated to iodine with 2-iodosobenzoate, and then converted into d-iodo-A. A dimethylanifine in the presence of A, A -dimethylanihne. The derivative was extracted into cyclohexane and determined by GC—mass spectrometry. The method could also be used to determine iodine by derivatization in the absence of 2-iodoso-benzoate, and iodate by its reduction with ascorbic acid to iodide and subsequent derivatization. The calibration graph was finear from 0.02 to 50p,g U of iodide with a correlation coefficient of 0.9998. The limit of detection was 8ng 1 of iodide. The proposed method was appfied to the determination of iodate in iodized table salt and free iodide and total iodine in seawater. The recovery was in the range of 96.8—104.3%, and the relative standard deviations were from 1.9% to 3.6%. A sample clean-up by solid-phase extraction with a LiChrolut EN cartridge was... 

A semi-automated method for determination of the total iodine in milk was described by Aumont (Aumont, 1982). The method involved destruction of organic matter by alkaline incineration and automated spectrophometric determination of iodide based on the Sandell and Kolthoff s reaction. The recoveries of the added iodide before calcination were between 90.05 +/- 7.36% and 97.14 +/- 4.56% (mean +/- S.D.). The coefficient of variation ranged from 2.15 to 7.21% depending on the iodine content in the milk. The limit of detection was estimated to be aroxmd 2 pg/kg. 

Another modification of the catalytic kinetic spectrophotometric method has been established for the determination of iodine using the principle that potassium periodate oxidize rhodamine B (RhB) to discolor and 1 has a catalytic effect on the reaction. The absorbance difference (AA) is linearly related with the concentration of iodine in the range of 0 - 2.6 pg/mL and fits the equation AA = 0.1578 C(C pg/mL) + 0.0052, with a regression coefficient of 0.9965. The detection limit of the method is 7.10 ng/mL. The method was used to determine iodine in kelp, potato, tap water, and rain water samples. The relative standard deviation of 13 replicate determinations was 1.81-2.10%. The recovery of the standard addition of the method was 96.2-99.2% (Zhaiet al., 2010). 

A flow injection method based on the catalytic action of iodide on the colour-fading reaction of the FeSCN2+ complex was proposed and applied in order to determine iodine in milk. At pH 5.0, temperature 32°C and measurements at 460 nm, the decrease in absorbancy of Fe -SCN (0.10 and 0.0020 mol /I) in the presence of N02" (0.3 mol/ 1) is proportional to the concentration of iodide, with a linear response up to 100.0 pg/1. The detection limit was determined as 0.99 pg/1 and the system handles 48 samples per hour. Organic matter was destroyed by means of a dry procedure carried out under alkaline conditions. Alternatively, the use of a Schoninger combustion after the milk dehydration was evaluated. The residue was taken up in 0.12 mol/1 KOH solubilization. For typical samples, recoveries varied from 94.5 to 105%, based on the amounts of both organic matter destroyed. The accuracy of the method was established by using a certified reference material (IAEA A-11, milk powder) and a manual method. The proposed flow injection method is now applied as an indicator of milk quality on the Brazilian market (de Araujo Nogueira et al., 1998). 

GC method has been developed for determination of total iodine in food, based on the reaction of iodine with 3-pentanone. Organic matter of a sample was destroyed by an alkaline ashing technique. Iodide in a water extract of the ash residues was oxidized in order to free I2 by adding Cr20/2- in the presence of H2SO4. Liberated iodine reacted with 3-pentanone to form 2-iodo-3-p>entanone, extracted into n-hexane, and then determined by gas chromatography with an electron-capture detector. Recoveries of L from spiked food samples ranged from 91.4 to 99.6%. Detection limit for iodine was 0.05 pg/g (Mitsuhashi KanedaY,1990). 

The second method uses preconcentration to increase the analyte concentration in the absorption solution to detectable levels prior to analysis. One example is the use of solid-phase extraction with an anion exchange column as a pretreatment technique to remove interference from the sample matrix and to enhance the detection sensitivity prior to determination of the concentrated iodide anion through reversed phase high-performance liquid chromatography (HPLC) using an ultraviolet (UV) detector. The results show more than 90% recovery and good reproducibility for the determination of trace iodine in iodine-enriched eggs. 

Molybdenum and tungsten. Oura et al. (2007) apphed postirradiation RNAA to determine trace amounts of Mo and W in geo- and cosmochemical samples. Samples were fused and Mo and W were separated from other elements by an anion resin. Chemical recoveries were determined by ICP-OES for both elements in each sample. To correct the Mo results for fissiogenic Mo resulting from fission of another fission product, i.e., I in each sample solution was determined by RNAA. Iodine was separated as Pdia precipitate. Under the given experimental conditions, detection limits of about 100 ppb for Mo and W were achieved. 

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