Determination of iodate

Determination of iodate as silver iodide Discussion. Iodates are readily reduced by sulphurous acid to iodides the latter are determined by precipitation with silver nitrate solution as silver iodide, Agl. Iodates cannot be converted quantitatively into iodides by ignition, for the decomposition takes place at a temperature at which the iodide is appreciably volatile. 

Truesdale [77] has described autoanalyser procedures for the determination of iodate and total iodine in seawater. The total iodine content of seawater (approximately 50-60 ig/l) is believed to be composed of iodate (30-60 xg/l of I) and iodine-iodine (0-20 xg/l) with perhaps a few ig/l of organically... 

Determinations of iodate without pre-oxidation in Pacific seawater by the previous method gave a mean result of 583 ig/l with a standard deviation of 0.23 xg/l. For samples containing between 40 and 60 xg/l, standard deviations of 0.19 xg/l (iodate method with pre-oxidation), 0.12 xg/l (iodate method without pre-oxidation), and 0.43 ig/l (total iodine method) were obtained. 

Truesdale and Smith [80] also carried out a comparative study of the determination of iodate in open ocean, inshore Irish seawaters and waters from the Menai Straits, using the spectrophotometric method (with and without pre-oxidation using iodine water) and also by a polarographic method [82]. 

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. 

Figure 4.2. Determination of iodate, bro mate, and bromide. From [12]... 

Kumar S. D., Maiti B. Mathur P. K. Determination of iodate and sulfate in iodized common salt by ion chromatography with conductivity detection. Talanta 2001 53(4) 701-705. 

Dietrich et al. [7] applied micelle exclusion chromatography to the determination of iodate, nitrite, nitrate, bromide and iodide in non saline waters. 

What conclusion may be drawn concerning the quantitative determination of iodate by the addition of acidified potassium iodide followed by titration with thiosulfate ... 

Inductively coupled plasma mass spectrometry has several inherent advantages over conventional detection techniques, including its sensitivity and element specificity. However, IC with inductively coupled plasma mass spectrometry was not used for the analysis of iodide and iodate in seawater, except in a very recent report (Chen et al.y 2007). This could be because the high concentration of matrices in seawater led to loss of sensitivity from the build-up of salts on the sampler and skimmer cones of the mass spectrometer. In addition, chloride interfered with eluting very near to iodate because the column was overloaded when the chloride concentration was very high in seawater. Recently, a nonsuppressed IC with inductively coupled plasma mass spectrometry was developed for simultaneous determination of iodate and iodide in seawater (Chen et al., 2007). An anion-exchange column... 

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... 

G. O. Aspinall and R. J. Ferrier, Spectrophotometric method for the determination of periodate consumed during the oxidation of carbohydrates, Chem. Ind. (London), (1956) 1216 J. X. Khym, Direct spectrophotometric determination of iodate following periodate oxidation of a-glycol groups, Methods Carbohydr. Chem., 6 (1972) 87-93. 

Silva et al. (Silva et al., 1998) outlined a new method for the determination of iodate in table salt. KIO3, after being converted to I3 by reacting with iodide in the presence of phosphoric... 

A solution of Ag precipitates IO3 as white silver iodate, AglOs, ciystalline, soluble in NH3, in excess of hot HNO3 and in HIO3. This may be dried and weighed for the determination of iodate. 

Abdalla, M. A. and H. M. Al-Swaidan. 1989. lodimetric determination of iodate, bromate, hypochlorite, ascorbic acid, and thiourea using flow-injection amperom-etry. Analyst 114 583-586. 

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