Determination of iodides

One of the most required methods of determination of iodide-ions in praetiee of ehemieal analysis is photometrie determination of produets of iodination of organie eompounds. The oxidation of iodide to iodine ean be earned out suffieiently seleetively. But in ease of presenee of great abundanee of bromide-ions the seleetive oxidation of iodide-ions is problematie. The variants of determination of iodide-ions with different organie reagents are known, but the absenee of bromide-ions in a system is supposed in most of them. In natural objeets these halides are present simultaneously. 

The seleetive method of determination of iodide-ions in the bromide-prevalenee systems is suggested. The variant is realized this way ... 

The eomparison of this variant of determination of iodide-ions with the method of speetrophotometrie deteimination of iodide-ions with lodinephenol Red is earried out. The seleetivity of determination of iodide-ions with lodinephenol Red is measured. The systematie errors appear signifieantly of C(Br) of6T0-"mol/l. 

The use of change of the balanced composition of the mixture depending from the reductive-oxidative potential is shown on the example of coulometric determination of iodides and bromides and spectrophotometric determination of iodides in the presence of bromides at electrochemical oxidation. 

Determination of iodide as silver iodide Discussion. This anion is usually determined by precipitation as silver iodide, Agl. Silver iodide is the least soluble of the silver halides 1 litre of water dissolves 0.0035 mg at 21 °C. Co-precipitation and similar errors are more likely to occur with iodide than with the other halides. 

Rendleman, J. A. (2003). The reaction of starch with iodine vapor. Determination of iodide-ion content of starch-iodine complexes. Carbohydr. Polym. 51,191-202. 

To date, a few methods have been proposed for direct determination of trace iodide in seawater. The first involved the use of neutron activation analysis (NAA) [86], where iodide in seawater was concentrated by strongly basic anion-exchange column, eluted by sodium nitrate, and precipitated as palladium iodide. The second involved the use of automated electrochemical procedures [90] iodide was electrochemically oxidised to iodine and was concentrated on a carbon wool electrode. After removal of interference ions, the iodine was eluted with ascorbic acid and was determined by a polished Ag3SI electrode. The third method involved the use of cathodic stripping square wave voltammetry [92] (See Sect. 2.16.3). Iodine reacts with mercury in a one-electron process, and the sensitivity is increased remarkably by the addition of Triton X. The three methods have detection limits of 0.7 (250 ml seawater), 0.1 (50 ml), and 0.02 pg/l (10 ml), respectively, and could be applied to almost all the samples. However, NAA is not generally employed. The second electrochemical method uses an automated system but is a special apparatus just for determination of iodide. The first and third methods are time-consuming. 

Sugawara [98] has described a spectrophotometric method for the determination of iodide in seawater. Various workers [99,100] have modified this procedure. 

Luther et al. [92] have described a procedure for the direct determination of iodide in seawater. By use of a cathodic stripping square-wave voltammetry, it is possible to determine low and sub-nanomolar levels of iodide in seawater, freshwater, and brackish water. Precision is typically 5% (la). The minimum detection limit is 0.1 - 0.2 nM (12 parts per trillion) at 180 sec deposition time. Data obtained on Atlantic Ocean samples show similar trends to previously reported iodine speciation data. This method is more sensitive than previous methods by 1-2 orders of magnitude. Triton X-100 added to the sample enhances the mercury electrode s sensitivity to iodine. 

Buchberger et al. [104] carried out a selective determination of iodide in brine. The performance of a potentiometric method using an ion-selective electrode and of liquid chromatography coupled with ultraviolet detection at 230 nm were compared as methods for the determination of iodide in the presence of other iodide species. Satisfactory results were obtained from the potentiometric method provided the solution was first diluted tenfold with 5 M sodium nitrate, and external standards were used. Better reproducibility was, however, achieved with HPLC, provided precautions were taken to prevent reduction of iodine to iodide in the mobile phase, for which extraction of iodine with carbon tetrachloride prior to analysis was recommended. This was the pre-... 

The classical method for the determination of iodide in seawater was described by Sugawara [5]. Various workers [6,7] have improved the original method. Matthews and Riley [6] modified the method by concentrating iodide by means of coprecipitation with chloride using silver nitrate (0.23 g per 500 ml seawater). Treatment of the precipitate with aqueous bromine and ultrasonic agitation promote recovery of iodide as iodate which [15] when reacted with excess of iodide ions under acid conditions, yields Ij, which are determined either spectrophotometrically or by photometric titration with sodium thiosulfate. Photometric titration gave a recovery of 99.0 0.4% and a coefficient of variation of 0.4% compared with 98.5 0.6% and 0.8%, respectively, for the spectrophotometric procedure. 

Pantiickova, P., and Kfivankova, L. (2004). Past and simple method for determination of iodide in human urine, serum, sea water, and cooking salt by capillary zone electrophoresis. Electrophoresis 25, 1102-1111. 

Iodide ion-selective electrode The iodide electrode has broad application both in the direct determination of iodide ions present in various media as well as for the determination of iodide in various compounds. It is, for example, important in the determination of iodide in milk [44,64,218, 382, 442], This electrode responds to Hg ions [150, 306, 439] and can be used for the indirect determination of oxidizing agents that react with iodide, such as 10 [305], lOi [158], Pd(II) [117, 347,405] and for the determination of the overall oxidant content, for example in the atmosphere [393], It can also be used to monitor the iodide concentration formed during the reactions of iodide with hydrogen peroxide or perborate, catalyzed by molybdenum, tungsten or vanadium ions, permitting determination of traces of these metals [12,192,193, 194, 195]. The permeability of bilayer lipid membranes for iodide can be measured using an I"... 

The determination of iodide with ion-selective electrodes is possible with commercial sensors often based on ion conducting Ag2S—Agl solid membranes [57]. A PVC membrane-based sensor employing a silver complex with thiourea derivatives has been reported by El Aamrani et al. [202]. Interference from thiocyanate and bromide was investigated and a limit of detection in the nanomolar range was determined. A study assessing the performance... 

Rebary B., Paul P. Ghosh P. K. Determination of iodide and iodate in edible salt by ion chromatography with integrated amperometric detection. Food Chemistry 2010 123(2) 529-534. 

Lacroix, D. E. and Wong, N. P. 1980. Determination of iodide in milk using the iodide specific ion electrode and its application to market milk samples. J. Food Protection 43, 672-674. 

This reaction may be employed for the determination of iodides 11 the iodine is expelled by heating and the equivalent amount of arsenious acid in the solution determined. 

The determination of iodide in milk (2% milkfat) by ion chromatography coupled with pulsed amperometric detection on a silver electrode is an application that benefits from matrix elimination of fats. The pulsed amperometric waveform improves reproducibility by electrochemically cleaning the working electrode on each pulse. In addition, the fats are removed from the sample using a disposable cartridge containing a polymeric reversed phase resin (OnGuard II RP, Dionex Corp.). When 50 jal of 0.1 mg/1 iodide was added to 200 jal of prepared milk, the recovery was 100%. The iodide peak area and retention time RSDs were 1.4% and 0.4% respectively [28]. 

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). 

In a more recent work Ito [101] has described a simple and highly sensitive ion chromatographic method with ultraviolet detection for determining iodide in seawater. A high-capacity anion exchange resin with polystyrene-divinylbenzene matrix was used for both preconcentration and separation of iodide. Iodide in artificial seawater (salinity, 35 % ) was trapped quantitatively (98.8 0.6%) without peak broadening on a preconcentrator column and was separated with 0.35M sodium perchlorate+ 0.10M phosphate buffer (pH 6.1). On the other hand, the major anions in seawater, chloride and sulphate ions, were partially trapped (5-20%) and did not interfere in the determination of iodide. The detection limit for iodide was 0.2pg L 1 for 6mL of artificial seawater. This method was apphed to determination of iodide (ND-18.3pg L ) and total inorganic iodine (I +I03 -I, 50.0-52.7pg L 1) in seawater samples taken near Japan. 

P. Bermejo Barrera, M. Aboal Somoza, A. Bermejo Barrera, M. L. Cervera, M. de la Guardia, Microwave assisted distillation of iodine for the indirect atomic absorption spectrometric determination of iodide in milk samples, J. Anal. Atom. Spectrom., 16 (2001), 382-389. 

Determination of Iodide with Silver Microelectrodes. Anal. Chem. 33, 325... 

Rong, L. and Takeuchi, T. 2004. Determination of iodide in seawater and edible salt by microcolumn liquid chromatography with poly(ethylene glycol) stationary phase. Journal of Chromatography A, 1042 131-5. 

Why does a Volhard determination of iodide ion require fewer steps than a Volhard determination of... 

In contrast to Ag2C03 and AgCN, the solubility of Agl is unaffected by the acidity. In addition, Agl is less soluble than AgSCN. The filtration step is thus unnecessary in the determination of iodide, whereas it is needed in the determination of carbonate or cyanide. 

Milk products Determination of iodide in whole milk chloride and/or sodium in butter lactate, pyruvate and citrate in cheese... 

Fig. 8-106. Amperometric determination of iodide in brine. — Separator column IonPac AS7 eluent 0.2 mol/L HN03 flow rate 1.5 mL/min detection amperometry at an iodated Pt working electrode oxidation potential +0.8 V injection 50 pL sample (diluted 1 10).

The catalytic effect of iodide on the oxidation of As(III) by Ce(IV) [25,26], and the oxidation of various organic substances by hydrogen peroxide [27-32] has been the basis of a number of kinetic methods for determination of iodide. 

Extraction of iodine (from oxidation of iodide) into CCI4 was applied in determination of iodide in sodium chloride [47] and in mercury(II) iodide [48]. Iodide was determined in seawater after oxidation to iodine and flotation into benzene [49]. 

M. Stoicheva, et. al., Voltammetric methods for determination of iodides in mineral water and iodized salt, Khranit.Prom-st. 39 (5), 28-9 (1990). 

A.N. Araujo, J.L.F.C. Lima, M.L.M.F.S. Saraiva, R.P. Sartini, E.A.G. Zagatto, A SIA system with mixing chamber for handling high concentrated solutions spectropho-tometric catalytic determination of iodide in nutrition salts, J. Flow Injection Anal 14 (1997) 151. 

Signal subtraction is more efficient when Schlieren component B prevails and the catalytic determination of iodide in table salts [119], highlighted in 3.1.2.2, illustrates this aspect. After sample passage through a mixing chamber, concentration discontinuities were eliminated and the influence of Schlieren component A became insignificant. Net absorbance values were precisely quantified on top of a very high (0.4 absorbance) yet reproducible blank value. Precise results (r.s.d. <4%) were then obtained. 

D. Nacapricha, K. Uraisin, N. Ratanawimamwong, K. Grudpan, Simple and selective method for determination of iodide in pharmaceutical products by flow injection analysis using the iodine-starch reaction, Anal. Bioanal. Chem. 378 (2004) 816. 

D. Nacapricha, P. Sangkarn, C. Karuwan, T. Mantim, W. Waiyawat, P. Wilairat, T. Cardwell, I.D. McKelvie, N. Ratanawimamwong, Pervaporation-flow injection with chemiluminescence detection for determination of iodide in multivitamin tablets, Talanta 72 (2007) 626. 

Nomura, T., Watanabe, M., and West, T. M. (1985). Behaviour of piezoelectric quartz crystals in solutions with application to the determination of iodide. Anal. Chim. Acta 175,107-112... 

Let us consider the determination of iodides as an example. The reaction method of iodide determination was proposed by Hasty [137, 138]. It is based on iodination of ketones in an acidic medium followed by determination of the resulting iodoketone by gas-liquid chromatography using an electron-capture detector. The method was later improved by using butanone-2 instead of acetone, which made it possible to increase the detection sensitivity [139]. A similar method for determining the total content of inorganic iodine in milk was proposed by Bakker [140]. The detection limit does not exceed lOmg/1. It is a sufficiently accurate method with a relative standard deviation of 1.9%. 

H. Muller, Determination of Iodide, Cyanide, Molybdenum(VI) and Tung-sten(VI) with the Flow-Through Iodide-Selective Electrode Using the Flow Injection Method. Anal. Chem. Symp. Ser., 18 (1984) 353. 

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