The determination of nano-amounts of iodine in waters,plants, foods,special diets,tissues, and soils

Summary A universal method for the determination of nano-amounts (ng= =10^–9 g) of iodine in various types of biological material is described. The recovery of added iodine standard averaged around 95%. The standard deviation for the method is ± 5%.

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Zusammenfassung Eine universelle Methode zur Bestimmung von Nanogramm-Mengen Jod in verschiedenen biologischen Materialien wird beschrieben. Zugesetzte Jodmengen wurden durchschnittlich zu 95% wiedergefunden. Die Standard-abweichung der Methode beträgt ±5%.

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Résumé On décrit une méthode universelle pour le dosage de quantités de l'ordre du nanogramme (1 ng=10^–9 g) d'iode dans les différents types de substance biologique. La concordance avec l'iode étalon ajouté atteint en moyenne 95% environ. La déviation standard de la méthode est de ±5%.

     

Ultra-trace determination of iodine in sediments and biological material using UV photochemical generation-inductively coupled plasma mass spectrometry

Several sample preparation techniques have been evaluated for the determination of iodine using UV-photochemical generation-quadrupole inductively coupled plasma mass spectrometry. Thermal decomposition of samples at 1000 °C followed by capture of the liberated iodine in dilute acetic acid permitted subsequent UV-photochemical generation of a volatile iodine species that serves to enhance sensitivity 25-fold over conventional solution nebulization, delivering reagent blank detection limits of 8.75 pg g^{–1 127}I and 0.075 pg g^–1 129I for solid samples (400 mg test mass). The methodology was validated through determination of total iodine in several Standard Reference Materials, including NIST 1572 Citrus leaves, NIST 1549 Non-fat milk powder, NIST 1566a Oyster tissue and NIST 2709 San Joaquin Soil. Liberation of iodine from samples and its collection as well as photochemical generation were quantitative, permitting calibration to be achieved using standards prepared in dilute acetic acid.     

Semi-automated determination of iodine in biological fluids by activation analysis

A simple automated system has been built that permits the selective separation of radioiodine by ion-exchange in eight samples simultaneously and the regeneration of the resin columns in fifteen minutes. Iodine is subsequently determined by γ-spectrometry.     

Rapid determination of total iodine in Japanese coastal seawater using SF-ICP-MS

A simple and rapid analytical method to measure total iodine in seawater using sector-filed ICP-MS is presented here. The new method avoided tedious and complicated organic iodine decomposing and redox treatment. In addition, no pre-concentration and separation operations are needed. The seawater was diluted 100-fold with 0.5% TMAH prior to SF-ICP-MS analysis. Te was added as internal standard. Due to the high sensitivity of SF-ICP-MS, excellent detection limit of 0.23 ng ml^? 1 in original seawater was obtained. By applying this newly developed method, for the first time, the total iodine concentrations in Japanese coastal seawaters in 14 estuaries were investigated. An average value of 58.26 ± 6.30 ng ml^? 1 (n = 59) for total iodine concentration was obtained for future study on the estimation of sediment–water distribution coefficients and the concentration ratios from water to organisms in Japanese coastal marine environment.     

The determination of iodine in biological and environmental standard reference materials

Iodine is an element with excellent intrinsic sensitivity when determined by thermal neutron activation. However, in most real samples, the preponderance of chlorine and bromine, relative to iodine, makes the direct determination of iodine virtually impossible. Over the past 20 years, there probably have been as many publications on the separation of iodine as there have been for any other radionuclide. Upon review, however, the methods are essentially the same. After irradiation, the samples are subjected to a rapid destructive process to free the iodine from the matrix and then the iodine is separated from the other halides either by liquid-liquid extraction or by liquid ion exchange. Both of these procedures are, however, rather complex and do not effect a complete separation of the halides in one pass. In the work presented here, a simple procedure is described for the quantitative separation of iodine from chlorine. The procedure utilizes a gas phase separation on hydrated manganese dioxide with iodine collected on silvered quartz wool. The described procedure has been used for the determination of iodine in numerous new and old SRM's at the NBS.     

Rapid one-step derivatization of Se(VI) to a piazselenol for the spectrofluorimetric determination of selenium in biological material

A spectrofluorimetric method for the determination of total selenium in biological samples has been developed. After oxidative destruction, the sample is reacted with a mixture of bromide and 2,3-diamino-1,4-dibromonaphthalene (Br₂-DAN) without pH adjustment. Selenium(VI) is rapidly reduced by bromide to Se(IV) which then forms 4,7-dibromo-5,6-benzopiazselenol (Br₂-DAN-Se). The conversion of Se(VI) to Br₂-DAN-Se is completed in 6 min at 100°C. The piazselenol is extracted to cyclohexane and the fluorescence measured at 577 nm with excitation at 518 nm. The procedure has been validated by determinations on reference materials with selenium concentrations ranging from 4 to 1460 ng g⁻¹. The advantages of the method are the fast reduction of Se(VI) by hydrobromic acid and the properties of Br₂-DAN, which permit the piazselenol formation to be carried out in a strongly acidic medium and at high temperature. The limit of detection is 0.6 ng g⁻¹ as estimated by three times the standard deviation of the blank determination (n = 7).

The rate of reduction of Se(VI) to Se(IV) in hydrobromic acid was investigated as a function of concentration and temperature. The new kinetic data together with previous kinetic and equilibrium data for the piazselenol formation were used to model and optimize the simultaneous reduction-derivatization procedure.     

Rapid microchemical method for the determination of magnesium in biological fluids

A photometric method for the determination of magnesium in the presence of up to 50-fold excess of calcium is described. A magnesium-Azovan Blue lake is formed, stabilized with polyvinyl alcohol, and the absorbance is measured (Kodak No. 7 filter). The method has been used to determine magnesium in sera.     

Simplified sample preparation for fluoride determination in biological material

A simple and rapid preparation method for the determination of fluoride in biological materials (blood and food) of various origins, is described. A homogenized sample was placed in a plastic diffusion cell and calcium phosphate added, it was then dried at 55 degrees C and treated with 70% HClO4 and 40% AgClO4. After digestion for 24 h at 55 degrees C, the fluorides released were fixed on the upper part of a diffusion cell containing a thin layer of NaOH. The analyses of the diffused fluoride were carried out with an ion-selective electrode. The proposed microdiffusion method, without mineralization, enables quantitative separation of the fluoride from the biological samples.     

A specific micromethod for the determination of phytic acid in biological material

A method for the quantitative determination of phytic acid in biological material is described. The method permits a determination of phytic acid in quantities below 0.1 mg even if the material contains closely related compounds includingmyo-inositol pentakisphosphate.

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Eine spezifische Mikromethode für die Bestimmung von Phytinsäure in biologischem Material

Zusammenfassung Es wird eine Methode zur quantitativen Bestimmung von Phytinsäure in biologischem Material beschrieben. Die Methode erlaubt die Bestimmung von Phytinsäure in Mengen von weniger als 0.1 mg, selbst wenn das Untersuchungsmaterial nahe verwandte Substanzen wie z. B.myo-Inositpentakisphosphat enthält.

     

Semi-automated fluorimetric determination of nanogram quantities of selenium in biological material

A semi-automated method, based on the solvent extraction and fluorescence of 4,5-benzopiazselenol, is described for the determination of selenium in biological material. Samples, in batches of up to 150, are digested in a mixture of nitric and perchloric acids in temperature-controlled aluminium blocks. Selenate formed in the perchloric acid is reduced to selenite with hydrochloric acid. Metal ion interferences, including hydroxide adsorption of selenite, are prevented by ethylenediaminetetraacetic acid. Sulphate above 50 mM precipitates the 2,3-diaminonaphthalene, so wool digests were diluted accordingly. The digests are analysed from their digestion tubes at the rate of 40 per hour by the semi-automated method. Results for blood and a variety of food samples compare favourably with those obtained by other methods including hydride/atomic absorption and instrumental neutron-activation analysis.     

A catalytic-kinetic method for the determination of traces of fluoride in biological material

A catalytic-kinetic method for the determination of nanogram amounts of fluoride, based on its inhibiting action on the catalyst in the zirconium-catalyzed reaction between perborate and iodide, is described. The rate measurements are accomplished very simply by using a Landolt reaction system with a biamperometric detection of the induction period. The standard deviation in the working range 19–190 ng of fluoride (1–10 nmol) is ± 2 ng. The method can be made specific by combining it with a separation of the fluoride by microdiffusion. This has been demonstrated by analyzing biological material and comparing the results with the fluoride contents obtained with other methods.     

A method for quantitative determination of deuterium content in biological material

A method was developed for quantitative determination of deuterium incorporated into live organisms or biological macromolecules. The deuterated biological material was mixed with a bovine serum albumin (BSA) supporter to make a homogeneous sample for which the deltaD value (vs. VSMOW) was analyzed using a dual-inlet gas isotope mass spectrometer. The method is described in detail, and the equation for calculation of deuterium content is presented, i.e., CbioD=1/500 x k x RVSMOW x CBSAH x 10(6) ppm. Deuterated hepatitis A virus (HAV) RNA and BSA were systematically investigated. The results demonstrate that the method is capable of direct measurement of deuterium content, and is highly repeatable and reliable with a standard deviation of +/-3 per thousand. It is stressed that the quantity of deuterated sample required is extremely small as a result of using BSA as supporter. The method may be applied in many fields, and has the strengths of simplicity, relative cheapness, and robustness.     

The determination of phanquone in biological material by gas-liquid chromatography.

A gas-liquid chromatographic method for the quantitative determination of phanquone is described, based on the formation of a dimethoxine prior to its extraction from biological material. The sensitivity of the procedure is about 15 ng/ml in biological fluid.     

Solvent extraction and radiometric determination of3H-stobadine in biological material

A simple and rapid radiochemical method for the efficient and selective isolation of³H-stobadine from plasma, urine and organ homogenates has been developed. The method comprises the extraction of³H-stobadine from the biological matrix containing 2M Na₂CO₃ into n-hexane followed by scrubbing of partly coextracted metabolites into an equal volume of 2M Na₂CO₃. The specificity of the procedure presented is demonstrated by TLC and the comparison of distribution coefficients of authentic and apparent (isolated) substances.     

TLC technique for the detection and determination of gamma- BHC in biological material

Summary Five isomers present in technical benzene hexachloride were successfully separated by TLC on silica-gel G impregnated with silver nitrate solution. The -isomer was identified by running a control sample of -BHC. Measurement of the spot area was found suitable for the estimation of 5–20g of-BHC, and was applied to analysis of autopsy tissues. The limit of identification is 0.1g.

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Zusammenfassung Auf mit Silbernitratlösung imprägniertem Kieselgel G konnten dünn-schichtchromatographisch fünf Isomere aus technischem Hexachlorbenzol erfolgreich getrennt werden. Das-Isomere wurde mit Hilfe einer Vergleichsprobe identifiziert. Die Planimetrie der Flecken eignet sich zur Schätzung von 5–20 g-Hexachlorbenzol. Die Methode wurde zur Untersuchung von Autopsieproben angewendet. Die Nachweisgrenze beträgt 0,1g.

     

Rapid determination of tricarboxylic acid cycle enzyme activities in biological samples

Background  

In the last ten years, deficiencies in tricarboxylic acid cycle (TCAC) enzymes have been shown to cause a wide spectrum of human diseases, including malignancies and neurological and cardiac diseases. A prerequisite to the identification of disease-causing TCAC enzyme deficiencies is the availability of effective enzyme assays.