Fractionation analysis of iodine in bovine milk by preconcentration neutron activation analysis

Iodine is an essential trace element for human beings. The main source of iodine is generally food items such as fish and milk. Either the lack or the excess of iodine can cause health problems. There exists an increasing interest in the determination of total iodine as well as various species of iodine in milk. We have developed an epithermal neutron activation analysis method with a Compton suppression (ENAA-CS) counting system for the determination of ng mL⁻¹ levels of iodine. We have also employed chemical separation methods prior to ENAA-CS to measure the fraction-specific concentrations of iodine in bovine milk. We have measured the following iodine concentrations in homogenized milk (3.25%milk fat): 0.48 ± 0.02 μg mL⁻¹ of total iodine, 0.020 ± 0.003 μg mL⁻¹ of lipid-bound iodine, 0.039 ± 0.002, 0.019 ± 0.002 and 0.021 ± 0.004 μg mL⁻¹ of protein-bound iodine depending on the protein separation method and 0.45 ± 0.02 μg mL⁻¹ of inorganic species.     

Simple and regioselective oxyiodination of aromatic compounds with ammonium iodide and Oxone

A simple method for the iodination of aromatic compounds using NH₄I as the iodine source and Oxone^® as the oxidant is described.     

Palladium-catalyzed oxidative allylic C-H silylation

Palladium-catalyzed allylic C-H silylation was performed with use of hexamethyldisilane as the silyl source. These C-H functionalization reactions occur only in the presence of hypervalent iodine reagents or other strong oxidants and proceed with excellent regioselectivity, providing the linear allylic isomer of the allylsilane products. In demonstrating the first oxidative allylic C-H silylation of alkenes, this study marks an important advance for the catalytic C-H functionalization method.     

Benzyl(triphenyl)phosphonium Dichloroiodate: A New Reagent for Coiodination of Alkenes

A mild, efficient, and regio‐ and stereoselective method for iodoalkoxylation and iodohydroxylation of olefins has been developed using benzyl(triphenyl)phosphonium dichloroiodate as iodine source. This procedure led to the corresponding iodoalkoxylated and iodohydroxylated products in moderate to excellent yields.     

Measurements of 127I M?ssbauer spectra for iodine compounds

127I M?ssbauer spectra of good quality were obtained at 20 K using a Zn127mTe source produced by high flux neutron irradiation of 66Zn-126Te at reactor core. The M?ssbauer spectra for KI and some iodine(III) compounds with absorption intensity of about 5% suggest that the 127I M?ssbauer spectroscopy is useful in elucidating the bonding nature of the iodine compounds. Preparative method of the M?ssbauer source and experimental technique are reported in detail.     

放射性同位素源X射线荧光法测量碘盐中碘含量

介绍用放射性同位素源激发Ｘ射线荧光法测定碘盐中碘的含量。方法简便、无损、快速、准确，可用于碘盐生产的产品质量监控。     

Iodine determination in dietary supplement products by TXRF and ICP-AES spectrometry

About two-thirds of the Hungarian population is living in areas where drinking water contains less than 0.025 mg/L I₂. Iodine is an essential element required for the synthesis of thyroid hormones. The recommended daily allowance (RDA) is 0.150 mg for adults (WHO [17]). In the case of iodine deficiency mineral water containing iodine and seaweed products could serve as the natural source of this element. In the present study, the capability and limitations of total reflection X-ray fluorescence (TXRF) and inductively coupled plasma atomic emission (ICP-AES) spectrometry for the determination of iodine are discussed, in the case of commercially available dietary supplements and differently processed seaweed (kelp) products. Multi-mineral tablets and kelp samples were digested using concentrated nitric acid before analysis. Extraction using a 25% ammonia solution was proved to be effective as an alternative sample preparation procedure for seaweed and dietary supplement tablets containing iodine. Precipitation of silver iodide, as a sample preparation step of mineral water, was applied to prevent loss of volatile iodine during solvent evaporation. ICP-AES measurement was found to be seriously affected by spectral line coincidence between the prominent line of iodine and the adjacent phosphorus line. TXRF was proved to be line coincidence free and suitable for iodine analysis. TXRF determination of iodine in mineral water, in seaweed samples and in dietary supplement tablets has not been reported yet.     

Oxidative iodination of carbonyl compounds using ammonium iodide and oxone®

A simple, efficient, mild, and regioselective method for oxyiodination of carbonyl compounds has been reported by using NH₄I as the source of iodine and Oxone® as an oxidant. Various carbonyl compounds such as aralkyl ketones, aliphatic ketones (acyclic and cyclic), and β-keto esters proceeded to the respective α-monoiodinated products in moderate to excellent yields. Unsymmetrical aliphatic ketones reacted smoothly yielding a mixture of 1-iodo and 3-iodo ketones with the predominant formation of 1-iodoproduct.     

Thallium-201 radioactive implant induced X-ray emission scanning of stable iodine distribution in thyroid--phantom experiment

A new method has been developed for imaging the thyroid gland by the use of 201Tl radioactive implant induced X-ray emission (RIXE). The thyroid phantom was made from two cylindrical tubes embedded in plastic neck phantom. Each tube consisted of stable iodine and 201Tl radioactive source in 10 ml water solution. Some photopeaks in the energy range from 20 to 200 ke V were scanned along a horizontal axis by the collimated Ge detector with high energy resolution. The distribution on the horizontal axis was obtained for the generated I K alpha-ray and some primary 201Tl radiations. The 201Tl RIXE scanning can provide information about the distribution of iodine with 201Tl as well as 201Tl distribution in the thyroid gland. The effectiveness of the 201Tl RIXE technique as a thyroid scanning method is discussed.     

Reactions in the source of a mass spectrometer: The mass spectrum of 1-chlorobenzotriazole

The mass spectrum of 1-chlorobenzotriazole contains ions derived from benzotriazole, a product of an exchange reaction with water in the source of the mass spectrometer. Relatively intense ions derived from iodine, iodine monobromide and other inter-halogen compounds are also observed. These species are produced by oxidation of involatile halide coatings in the source region by 1-chlorobenzotriazole. It is suggested that anomalous peaks produced by oxidation-reduction reactions in the source may be expected in the spectrum of any organic oxidant.     

Eco-friendly oxyiodination of aromatic compounds using ammonium iodide and hydrogen peroxide

A new eco-friendly procedure for the oxyiodination of aromatic compounds with NH₄I as an iodine source and H₂O₂ as an oxidant without any catalyst is presented.     

Generation of 4-iodoisocoumarins through a TBAI-mediated oxidative cyclization of 2-alkynoates

A tetra-butylammonium iodide (TBAI)-mediated oxidative iodocyclization of 2-alkynoates for the synthesis of various 4-iodoisocoumarin is described herein, and the reaction is highly efficient and shows broad functional group tolerance. This newly developed reaction uses a mixture of water and DCE as co-solvent, and avoids the use of iodine as iodine source for the electrophilic halocyclization.     

Ab initio study of hydroxyl torsional barriers and molecular properties of mono- and di-iodotyrosine

Phenol rings with one or two iodine atoms bonded to ortho carbons are the essential organic source of iodine for living organisms. The salvage of this halogen fundamental for a variety of biological functions is accomplished through enzymatic processes that rely on recognition of mono- and di-iodotyrosine (MIT and DIT, respectively). Ab initio quantum calculations are used to investigate molecular properties of MIT and DIT associated with their recognition by cognate proteins. Energies, electron density properties, atomic charges, and electrostatic potentials are analyzed in relation with the presence of one or two iodine atoms and internal rotation of hydroxyl hydrogen. The formation of an intramolecular hydrogen bond at some conformations has little effect on the properties that might affect the recognition and further deiodination of MIT and DIT. Polarizability of iodine and the reactive nature of iodinated tyrosines as nucleophilic targets are the essential features revealed in this work.     

Determination of iodine in diverse botanical and dietary matrices by pre-irradiation combustion followed by neutron activation analysis

Summary The method chosen for determination of iodine in this investigation is an extension of an existing analytical technique to food samples which was developed for environmental samples. The method is based on pre-irradiation combustion of the sample to liberate iodine, trapping the iodine on charcoal, and quantitating the element by neutron activation analysis (NAA). Existing botanical and dietary reference materials were used to check the validity of the method. Several mixed diet samples with high fat content from the U.S. Total Diet Study and composites of cereals with both low and high iodine content were analyzed. This method of pre-irradiation combustion followed by NAA has been shown to be a viable technique for the determination of iodine in dietary samples. However, with a detection limit of about 50 ng of iodine, large amounts of sample (>1 g) are typically required for each determination.     

Spectroscopy in separated flames--VII: Determination of bismuth by atomic-fluorescence spectroscopy in a separated air-acetylene flame with electronically modulated electrodeless discharge tube sources

The application of electronically modulated and unmodulated bismuth and iodine electrodeless discharge lamps as sources for the excitation of bismuth atomic fluorescence in conventional and nitrogen-separated air-acetylene flames has been investigated. Separation of the flame results in improved detection limits for bismuth even when a modulated source is employed. The effect of 500-fold weight excesses of foreign ions on the determination of bismuth at 302.46 nm with a modulated iodine source and separated flame has been studied; only calcium and zirconium are found to cause significant interference. The determination of bismuth in aluminium alloy samples is reported.     

Chemical template directed iodine patterns on the octadecyltrichlorosilane surface

A carboxylic-terminated nanometer-scale chemical pattern on an octadecyltrichlorosilane (OTS) surface can guide the deposition and crystallization of iodine, forming an iodine pattern on the chemical pattern. The iodine in the pattern is gel-like when fabricated by the solution-deposit method. In contrast, a dendritic, snowflake-shaped polycrystalline iodine sheet is formed by the vapor-phase condensation method. The data demonstrate that iodine is a good tracing and visualizing agent for studying liquid behavior at the nano scale. The topography of the iodine stain reveals that the "coffee ring" effect can be suppressed by reducing the pattern size and increasing the evaporation rate. The chemical template-bound iodine pattern has an unusually low vapor pressure and it can withstand prolonged baking at elevated temperature, which differs significantly from bulk iodine crystals.     

Determination of iodine in organic iodine compounds by non-equilibrium isotope exchange in a heterogeneous exchange system

Some water-soluble organic iodine compounds (aqueous solution) can be analyzed for iodine by isotopically exchanging with labelled elementary iodine (organic solution). The method is applicable to exchange systems in which the rate of the exchange is rather small but measurable, before the exchange equilibrium is attained. The iodine content of iodoaromatic amino acids such as 5-iodouracil and 3,5-diiodotyrosine can be determined within an error of ±4%.     

Simple spectrophotometric and titrimetric methods for the determination of sulfur dioxide.

The proposed work describes a simple spectrophotmetric as well as a titrimetric method to determine sulfur dioxide. The spectrophotometric method is based on a redox reaction between sulfur dioxide and iodine monochloride obtained from iodine with chloramine-T in acetic acid. The reagent iodine monochloride oxidizes sulfur dioxide to sulfate, thereby reducing itself to iodine. Thus liberated iodine will also oxidize sulfur dioxide and reduce itself to iodide. The obtained iodide is expected to combine with iodine to form a brown-colored homoatomictriiodide anion (460 nm), which forms an ion-pair with the sulfonamide cation, providing exceptional color stability to the system under an acidic condition, and is quantitatively relatd to sulfur dioxide. The system obeys Beer's law in the range 5 - 100 microg of sulfur dioxide in a final volume of 10 ml. The molar absorptivity is 5.03 x 10(3) l mol(-1)cm(-1), with a relative standard deviation of 3.2% for 50 microg of sulfur dioxide (n = 10). In the titrimetric method, the reagent iodine monochloride was reduced with potassium iodide (10%) to iodine, which oxidized sulfur dioxide to sulfate, and excess iodine was determined with a thiosulfate solution. The volume difference of thiosulfate with the reagent and with the sulfur dioxide determined the sulfur dioxide. Reproducible and accurate results were obtained in the range of 0.1 - 1.5 mg of sulfur dioxide with a relative standard deviation of 1.2% for 0.8 mg of sulfur dioxide (n = 10).     

Iodine determination in biological materials Options for sample preparation and final determination

This paper describes the development of various new acid sample decomposition methods, as well as an extraction (leaching) method and compares them with the “Sch?niger Combustion” technique. The methods have been developed as sample preparation techniques for iodine determination in biological materials, especially in solid samples. ICP-MS (inductively coupled plasma mass spectrometry) and a catalytic technique are employed and discussed for the final determination of iodine concentrations. Accuracy and reliability of the different analytical methods are shown in the examples of different CRMs (certified reference materials) available for iodine. The results of an interlaboratory comparison are specifically presented for the extraction (leaching) method. Received: 11 May 1998 / Revised: 14 June 1998 / Accepted: 16 June 1998     

Sensitive determination of bromine and iodine in aqueous and biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry using tetramethylammonium hydroxide as a chemical modifier

A procedure for the simultaneous determination of bromine and iodine by inductively coupled plasma (ICP) mass spectrometry was investigated. In order to prevent the decrease in the ionization efficiencies of bromine and iodine atoms caused by the introduction of water mist, electrothermal vaporization was used for sample introduction into the ICP mass spectrometer. To prevent loss of analytes during the drying process, a small amount of tetramethylammonium hydroxide solution was placed as a chemical modifier into the tungsten boat furnace. After evaporation of the solvent, the analytes instantly vaporized and were then introduced into the ICP ion source to detect the (79)Br(+), (81)Br(+), and (127)I(+) ions. By using this system, detection limits of 0.77 pg and 0.086 pg were achieved for bromine and iodine, respectively. These values correspond to 8.1 pg mL(-1) and 0.91 pg mL(-1) of the aqueous bromide and iodide ion concentrations, respectively, for a sampling volume of 95 microL. The relative standard deviations for eight replicate measurements were 2.2% and 2.8% for 20 pg of bromine and 2 pg of iodine, respectively. Approximately 25 batches were vaporizable per hour. The method was successfully applied to the analysis of various certified reference materials and practical situations as biological and aqueous samples. There is further potential for the simultaneous determination of fluorine and chlorine.