Iodide, iodine total

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. 

Nakayama, E., Kimoto, T., Isshiki, K., Sohrin, Y. and Okazaki, S. (1989) Determination and distribution of iodide and total-iodine in the North Pacific Ocean by using a new automated electrochemical method. Mar. Chem., 27, 105-116. 

In environmental waters, the most important oxidation states are iodide ( — 1) and iodate ( + 5). Most published methods for the analysis of radioiodine aim only to convert all species to one chemical form in order to determine a total concentration value for the particular nuclide of interest. However, some specialist methods designed for the analysis of the stable element such as that recently described by Woittiez et al. (1991) for the determination of iodide, iodate, total inorganic iodine and charcoal-absorbable (organic) iodine in seawater could presumably be adapted to provide information about the speciation of radioiodine as well. More difficult to adapt would be techniques such as polarography which have been useful in the measurement of the iodide/iodate system (e.g. Liss et al., 1973). 

Solution a contained iodine and silver nitrate together with perchloric acid and sodium perchlorate. Solution contained sodium iodide, iodine, perchloric acid, and sodium perchlorate. Both solutions had a total ionic concentration equal to 1.0 mole 1 and contained the same concentration of perchloric acid. The object of the acid was to suppress the formation of h3qx)iodous acid according to the equilibrium... 

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... 

Fuge, R., Johnson, C. C. (1986).The geochemistry of iodine - a review. Environmental Geochemistry and EIealth,Yo. 8, No. 2, pp 31-54, ISSN 0269-4042 Gamallo-Lorenzo,D., Barciela-Alonso, M. C., Moreda-Pineiro, A., Bermejo-Barrera, A. Bermejo-Barrera, P. (2005). Microwave-assisted alkaline digestion combined with microwave-assisted distillation for the determination of iodide and total iodine in edible seaweed by catalytic spectrophotometry. Analitka Chimica Acta, Vol. 542, pp 287-295, ISSN 0003-2670... 

Reduction of iodate to iodide before total iodine analysis was necessary because the species had different sensitivities by ICP-MS. Gradient elution with 5 mM KNO3... 

The table shows the initial partial pressures and the partial pressures at equilibrium of hydrogen, iodine and hydrogen iodide. The total pressure was constant throughout the experiment. 

Acute inhibitory effects of excess iodide was first demonstrated in vitro in 1944 by Morton, Chaikoff and Rosenfeld (i) and in vivo in 1948 by Wolff and Chaikoff (Wolff-Chaikoff effect) (2). As shown in Fig. 1, they injected 100 pg of iodide per rat with a tracer dose of and determined pleisma inorganic iodide concentration, total thyroidal iodine uptake and thyroidal organic iodine uptake until 50 hours after the injection of iodide. Thyroidal organic iodine... 

The hberated iodine is measured spectrometricaHy or titrated with Standard sodium thiosulfate solution (I2 +28203 — 2 1 VS Og following acidification with sulfuric acid buffers are sometimes employed. The method requires measurement of the total gas volume used in the procedure. The presence of other oxidants, such as H2O2 and NO, can interfere with the analysis. The analysis is also technique-sensitive, since it can be affected by a number of variables, including temperature, time, pH, iodide concentration, sampling techniques, etc (140). A detailed procedure is given in Reference 141. 

Sample decomposition is the critical operation in determination of total iodine in complex organic matrix. Iodine in simple form (I ) is highly volatile, so it should be transformed into nonvolatile analytical fomi (iodide or iodate) to prevent loses during the decomposition. 

Arkel refining a sample of tire impure metal, for example zirconium, is heated to a temperature around 550 K in contact with low pressure iodine gas in a sealed system which has a heated mngsten filament in the centre. The filament temperature is normally about 1700K. At the source the iodides of zirconium and some of the impurities are formed and drese diffuse across the intervening space, where tire total pressure is maintained at 10 auiios, and are decomposed on the filament. The iodine then remrns to form fresh iodide at the source, and the transport continues. 

A fresh sample of this 40% peracetic acid contains about 1.54 equivalents, or 0.77 mole, of peroxide per 100 ml. of solution, corresponding to 1.34 equivalents per 100 g. The concentration can be determined by treating the peroxide solution with potassium iodide and titrating the liberated iodine with standard sodium thiosulfate. The concentration of peroxide in peracetic acid decreases somewhat on long standing and should be checked before the peracetic acid is used. The yield of diacetate is lowered if the concentration of the peroxide is less than 1.0 equivalent per 100 g. of peracetic acid. The total amount of peroxide used should be 2.4 moles, or 4.8 equivalents, for each mole of iodo-benzene. 

More interesting was the elemental analysis of the residue. Whereas a 2 1 AcOH [DMEpy]l should have contained 33% iodine, the elemental analysis indicated the residue contained only 0.7% iodine. This clearly indicated that we no longer had an iodide salt, but more likely had an acetate salt, most likely a 2 1 mixture of AcOH [DMEpy] [OAc]. (The formation of a 2 1 salt would be typical of our experience with ionic liquids. In practice they normally tenaciously retain ca. 2 mol AcOH/mol of ionic liquid, a phenomena we noted in om earlier reports. (3) Closer comparison of the salt obtained and low levels of Mel detected in the effluent indicated that the amount of [DMEpy] [OAc] generated closely matched the total Mel (ca. 90-95% yield of Mel based on [DMEpy][OAc].) Further, the elemental analysis was unable to detect any Rh in the effluent, so we could conclude that there was no aspiration occurring. This clearly indicated that our ionic liquid loss was due to metathesis of the ionic liquid from the iodide to the acetate salt, likely due to reaction (23) which likely sublimed overhead. In principle, the miniscule amount of Mel and ionic liquid could be returned to the reactor to maintain the process. 

It has not yet been possible to obtain samples of amylopectin which do not show some slight evidence of uptake of iodine by linear material in the early stages of an accurate potentiometric titration. Although this effect is presumably due to contaminating amylose, the presence of some long branches in the amylopectin cannot be excluded. Anderson and Greenwood190 have shown that in 0.01 M iodide solution, for concentrations of total free iodine less than 1 X 10-6 M, the amount of iodine bound by... 

Schnepfe [83] has described yet another procedure for the determination of iodate and total iodine in seawater. To determine total iodine 1 ml of 1% aqueous sulfamic acid is added to 10 ml seawater which, if necessary, is filtered and then adjusted to a pH of less than 2.0. After 15 min, 1 ml sodium hydroxide (0.1 M) and 0.5 ml potassium permanganate (0.1M) are added and the mixture heated on a steam bath for one hour. The cooled solution is filtered and the residue washed. The filtrate and washings are diluted to 16 ml and 1ml of a phosphate solution (0.25 M) added (containing 0.3 xg iodine as iodate per ml) at 0 °C. Then 0.7 ml ferrous chloride (0.1 M) in 0.2% v/v sulfuric acid, 5 ml aqueous sulfuric acid (10%) - phosphoric acid (1 1) are added at 0 °C followed by 2 ml starch-cadmium iodide reagent. The solution is diluted to 25 ml and after 10-15 min the extinction of the starch-iodine complex is measured in a -5 cm cell. To determine iodate the same procedure is followed as is described previously except that the oxidation stage with sodium hydroxide - potassium permanganate is omitted and only 0.2 ml ferrous chloride solution is added. A potassium iodate standard was used in both methods. 

Iodine is present in the environment predominantly in the oxidation states —1 (1, iodide) and - -5 (lOs", iodate). Reduction of lOs" to 1 occurs at pe = 13.3 at pH 5 and pe° = 11.3 at pH 7. Hence 1 is expected to predominate in the soil solution except in oxic alkaline soils (Whitehead, 1984). However Yuita (1992) found predominantly IO3 in acid Japanese soils contaminated with iodine the concentrations in solution were some 20 times those of 1 and I2. On flooding the soils, the total concentration of 1 in solution increased 10- to 50-fold, predominantly as I. The concentrations of sorbed 1 were not measured, but both lOs and 1 are expected to be bound to organic matter and oxides and hence their concentrations in solution are expected to increase with reductive dissolution reactions. Further, for a given concentration in solution, 1 is more rapidly absorbed by plants than IO3 (Mackowiak and Grossl, 1999). Hence flooding is expected to increase accumulation in plants both through increased solubility and increased absorption. 

Sulfur dioxide in the sample causes a negative interference of approximately 1 mole of ozone per mole of sulfur dioxide, because it reduces the iodine formed by ozone back to potassium iodide. When sulfur dioxide concentrations do not exceed those of the oxidants, a method commonly used to correct for its interference is to add the amount of sulfur dioxide determined by an independent method to the total detector response. A second method is to remove the sulfur dioxide from the sample stream with solid or liquid chromium trioxide scrubbers. Because the data on the performance or these sulfur dioxide scrubbers are inadequate, the performance for each oxidant system must be established experimentally. 

By definition POV is the number of miliequivalents of active oxygen per kilogram of sample" , or in some cases the number of micrograms of active oxygen in one gram of sample, capable of oxidizing iodide to iodine" °°. Many of the methods described in Section V for determination of hydroperoxide classes or individual compounds can also be applied for determination of POV, as total hydroperoxides. The iodometric determination of hydroperoxides in lipids and proteins has been reviewed . 

Native urine should be protected from light and stored at -20°C until processed. Oxidized urine sample can be stored at room temperature, but light protection is still recommended. Two procedures for the oxidation of urine (and other samples) are used (1) oxidation with manganese dioxide (Mn02) under acidic conditions, and (2) oxidation with iodine (iodine/potassium iodide, I2/KI) under acidic and basic conditions. The Mn02 oxidation method is a routine method used to quantify total pterins (fully oxidized neopterin, monapterin, biopterin, primapterin, isoxanthopterin, and pterin) the I2/KI method is used according to Fukushima and Nixon [11] for the differential oxidation of pterins and quantification of BH4. Total biopterin represents the sum of BH4, BH2, and fully oxidized biopterin. Under acidic conditions BH4 and BH2 are oxidized to biopterin, while under basic conditions only BH2 is oxidized to... 

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