89Sr/90Sr-Determination in soils and sediments using crown ethers for Ca/Sr-separation

A radiochemical procedure is described for the sensitive determination of⁸⁹Sr and⁹⁰Sr activity concentrations in soil and sediment samples. After leaching the sample with hydrochloric acid, Sr is separated from most of the soluble matrix constituents and Ca by solvent extraction using dicylclohexano-18-crown-6 in trichloromethane. After backextraction with a EDTA-solution (ethylene diamine tetra acetate), Sr is purified by several precipitation steps from traces of matrix constituents and radionuclides which might interfere the beta measurements of⁸⁹Sr,⁹⁰Sr and⁹⁰Y. The detection limits are about 0.2 Bq/kg and 0.4 Bq/kg for⁹⁰Sr and⁸⁹Sr respectively. The procedure can be applied to all kind of environmental samples with small modifications of the sample preparation steps prior to analysis.     

Affinity Chromatography of Ribitol Dehydrogenase,a Possible New Zinc Enzyme from Mycobacterium Butyricum

Abstract

An effective purification procedure of ribitol dehydrogenase (RDH), a possible new zinc enzyme from Mycobacterium butyricum is described. The procedure took advantage of different chromatographic methods in which the most significant were two affinity chromatography steps. One of them was the immobilized metal ion affinity chromatography (IMAC), with the use of iminodiacetate-Sepharose 6B (IDA-Sepharose 6B) chelating Zn²⁺ ions (IDA-Zn) as an affinity sorbent. The enzyme was eluted with a decreasing pH gradient from 7 to 4. The other step was a biospecific affinity chromatography, where the enzyme retained on 5′ AMP-Sepharose 6B was eluted with 10 mM adenosine 5′-monophosphate (AMP). RDH was purified 174-fold with 10.2% of recovery, and the final preparation was homogenous in polyacrylamide gel electrophoresis.     

Radiochemical determination of chromium in biological tissues by ion-exchange

A simple ion exchange procedure has been developed for the separation of chromium from the other chemical elements in biological tissues. This procedure combined with neutron activation analysis has been applied successfully to the determination of chromium in a reference biological material. The precision was ±11%, the accuracy 3% and the sensitivity found was 10 ng with only 20 hrs irradiation at 2.8·10¹³ n·cm⁻²·sec⁻¹ flux The main steps of the procedure are: wetdigestion of the irradiated tissue, oxidation to chromium (VI), fixation onto an anion resin in sulfate form, washing of the resin with 1N H₂SO₄, collection of chromium by reductive elution for counting and finally determination of the chemical yield by reactivation.     

Comparison of Two Sequential Extraction Procedures for Trace Metal Partitioning in Sediments

Abstract

Two sequential extraction schemes (a modified Tessier procedure with five steps and a three steps protocol designed by BCR) are applied to four sediment samples with different heavy metal contents. The results obtained for Cd, Cr, Cu, Ni, Pb and Zn partitioning show that the metal distribution obtained with both procedures are significantly different. With the second procedure amounts of all the heavy metals are extracted with the oxidizing reagent (third fraction) whereas with the first one the non residual metals are distributed among the second, third and fourth fractions (acetic acid-acetate buffer (pH=5), reducing and oxidizing reagents respectively). The residual fraction obtained applying the three steps procedure is in general higher than that obtained using the five steps procedure, except for cadmium.     

Natural radioactivity in building materials utilized in the State of Kuwait

A simple radiochemical procedure is described for the determination of⁹⁰Sr in brines, which are very highly concentrated in sodium, calcium, potassium, magnesium, chloride and sulfate ions. The method is based on the different solubility of yttrium as compared to that of strontium, calcium and magnesium in ammonium chloride solutions, and utilizes Eichroms resin TRU·Spec for the purification of the yttrium fraction. The overall time required for the⁹⁰Sr analysis (excluding the counting time) is less than one day. Because the procedure involves only rather simple steps, it is well suited for routine analyses of large sample numbers.     

Implementation of a Sequential Injection Pre-Treatment Method for Simultaneous Radium and Strontium Determination

A semi-automatic procedure for the simultaneous determination of Ra and Sr in two steps has been developed. In the first step, separation and pre-concentration of both analytes is performed by using a sequential injection procedure. In the second step, the activities of ²²⁶Ra and ⁹⁰Sr, alpha and beta emitters, respectively, are determined using a low background proportional counter at the corresponding plateau potentials. ²²⁶Ra concentration is obtained by a single measurement of the precipitate. ⁹⁰Sr activity is determined by means of its daughter ⁹⁰Y carrying out two different measurements along the first day after the separation process; the solution of the Bateman radioactivity decay equations allows to obtain the initial ⁹⁰Sr-⁹⁰Y activities. The activities analysed in the present work have been ranged between 0-14 Bq/L for ²²⁶Ra and 0-175 Bq/L for ⁹⁰Sr.     

Application of Double Deposition and Stripping Steps System for Minimization of Interferences of Peaks’ Overlapping in Anodic Stripping Voltammetry

An anodic stripping voltammetric procedure for the determination of bismuth in the presence of excess of Cu²⁺ ions at two ex situ plated gold film electrodes was described. The procedure is based on utilization of two deposition and two stripping steps system. The presented procedure ensures increasing the sensitivity of Bi³⁺ determination and minimization of interferences related to peaks’ overlapping. The calibration graph for bismuth determination was linear from 2.5×10⁻⁹ to 2×10⁻⁸ mol L⁻¹ for deposition time of 300 s at both working electrodes while detection limit was 7.7×10⁻¹⁰ mol L⁻¹.     

Dispersion and states of platinum ions in BEA-zeolite pores: effect of the framework basicity

Pt/Cs-BEA materials prepared by a classical ion-exchange procedure using two Cs-BEA supports with different Cs loadings, and a reference acidic Pt/H-BEA, have been studied to investigate the effect of the framework basicity (evaluated by FT-IR of adsorbed CO₂) on the state of platinum species after the initial steps (introduction of Pt complex by ion-exchange and subsequent calcination) of the preparation procedure. DR-UV data revealed that the framework basicity affects the structure of the Pt²⁺ complexes introduced as countercations in the zeolite by ion exchange. FT-IR spectra of adsorbed CO indicated that zeolite basicity rules the fate of platinum species in the subsequent calcination. Hence, in Pt/H-BEA essentially well dispersed Pt^δ+ (4≥δ≥1) are present, while PtO _x particles progressively prevail as the basic character of the zeolite increases.     

Seasonal variations of atmospheric210Pb and7Be concentrations at Kumamoto, Japan and their removal from the atmosphere as wet and dry depositions</p> </p>

Summary A relatively simple chemical separation procedure has been developed for the simultaneous determination of⁸⁹Sr and ⁹ 0Sractivities in water samples and on aerosol-filters of the Nuclear Power Plant (NPP) Paks origin. The procedure combines the cation-exchange chromatographic (Dowex 50 WX 8 resin) and solid phase extraction (EIChroM Sr.Spec?, DC18C6 crown ether) steps. The beta-radiation of radionuclides can be measured directly after the chemical separation by LSC. The activities of⁸⁹Sr,⁹⁰Sr and⁹⁰Y are calculated from an over determined set of equations using a method of constrained optimization technique. The equations are based on LSC measurements performed in three counting windows plus the⁹⁰Sr-⁹⁰Y decay law. The chemical yield of strontium is determined by ICP-AES. The lowest limits of detectable activity, for the measurement time of 600 minutes, are 30 mBq/sample and 18 mBq/sample for⁸⁹Sr and⁹⁰Sr, respectively.     

Intermolecular Amination of Unactivated C(sp3)−H Bonds with Cyclic Alkylamines: Formation of C(sp3)−N Bonds through Copper/Oxygen‐Mediated C(sp3)−H/N−H Activation

The first example of intermolecular amination of unactivated C(sp³)?H bonds by cyclic alkylamines mediated by Cu(OAc)₂/O₂ is reported. This method avoids the use of benzoyloxyamines as the aminating reagent, which are normally prepared from alkylamines in extra steps. A variety of unnatural β^{2, 2}‐amino acid analogues are synthesized by this simple and efficient procedure. This approach offers a solution to the previous unmet challenge of C(sp³)?H/N?H activation for the formation of C(sp³)?N bonds.     

Quality control strategy for the determination of 210Po

A quality control programme is presented for the determination of ²¹⁰Po in samples from the phosphate ore-processing industry. Accuracy and precision of selected steps of the analytical procedure are quantified and the change in these parameters is monitored by analysis of hundreds of reference samples during the last two years.     

Separation of radioactive strontium from natural samples by means of mixed-solvent anion exchange

A new procedure for isolation and determination of⁹⁰Sr in real natural samples is presented. It consists of bringing natural samples in a soluble form suitable for separation on an ion-exchange column, separation of calcium from strontium by means of the anion exchanger Amberlite CG-400 and 0.25M HNO₃ in methanol as eluent for calcium, and the determination of⁹⁰Sr using a low level -counter after elution with H₂O, scavenging steps and SrCO₃ precipitation. The method was tested with IAEA standards of natural samples with known contents of⁹⁰Sr, and water samples, where the concentration of⁹⁰Sr was previously determined by the standard IAEA procedure. The results obtained show that it is possible to isolate and determine low levels of⁹⁰Sr in natural samples. The procedure is favorable because of the simple separation of radioaactive strontium without using fuming nitric acid.     

Losses of technetium during various steps in the development of a procedure for environmental samples

A key aspect of the development of a procedure for the measurement of technetium in environmental samples is that each step should be optimized to achieve maximum recovery.⁹⁹Tc and^95mTc have been the tracers used for the determination of yields in steps involving anion exchange, leaching, ashing, solvent extraction, precipitation and evaporation. The results thus obtained are discussed.     

SI-traceable certification of the amount content of cadmium below the ng g–1 level in blood samples by isotope dilution ICP–MS applied as a primary method of measurement

The development and implementation of a method for the certification of cadmium in blood samples at low ng g^–1 and sub ng g^–1 levels is described. The analytical procedure is based on inductively coupled plasma isotope dilution mass spectrometry (ICP–IDMS) applied as a primary method of measurement. Two different sample digestion methods, an optimized microwave digestion procedure using HNO₃ and H₂O₂ as oxidizing agents and a high-pressure asher digestion procedure, were developed and compared. The very high salt content of the digests and the high molybdenum content, which can cause oxide-based interferences with the Cd isotopes, were reduced by a chromatographic matrix separation step using an anion-exchange resin. All isotope ratio measurements were performed by a quadrupole ICP–MS equipped with an ultrasonic nebulizer with membrane desolvator. This sample introduction set-up was used to increase sensitivity and minimize the formation of oxides (less MoO⁺ interference with the Cd isotopes). Because of the very low Cd concentrations in the samples and the resulting need to minimize the procedural blank as much as possible, all sample-processing steps were performed in a clean room environment. Detection limits of 0.005 ng g^–1 Cd were achieved using sample weights of 2.7 g. The method described was used to re-certify the cadmium content of three different blood reference materials from the Community Bureau of Reference (BCR) of the European Commission (BCR-194, BCR-195, BCR-196). Cadmium concentrations ranged between ～0.2 ng g^–1 and ～12 ng g^–1. For these materials, SI-traceable certified values including total uncertainty budgets according to ISO and Eurachem guidelines were established.     

156Dy as an activable yield tracer for determination of rare earth elements in biological materials by neutron activation analysis

Use of an enriched¹⁵⁶Dy isotope as an activable yield tracer for the determination of lanthanoid contents in various biological reference materials has been proposed. The method consists of preconcentration of the lanthanoid in the¹⁵⁶Dy doped samples followed by neutron irradiation and further chemical purification steps. The chemical behaviour of lanthanoid elements in the whole procedure was found, in separate runs, similar to that of the added¹⁵⁶Dy within experimental errors. Simple purification steps after irradiation allow the measurement of relatively short-lived nuclides and diminish the radiation dose received during the chemical treatment. The present results for orchard leaves (NBS SRM 1571) are generally in good agreement with the previously reported data. Some new data are obtained for other biological reference materials.     

Regioselective α(2→3)-Sialylation of LeX and Lea by Sialidase-Catalyzed Transglycosylation

Considerable effort has been devoted to the development of new methods for α-selective sialylation due to the growing importance of the synthetic sialoglycoconjugates in glycobiology³. The synthesis of α-sialoside has been establised by chemical routes,⁴ which often involve many steps and are complicated. The promising chemoenzymatic procedure through the use of sialyltransferases has already become a preparative technique.⁵ However, laborious isolation and the pronounced acceptor specificity of the transferases limit their synthetic potential. Recently, a novel procedure for α-sialylation has been reported, which uses sialosides of synthetic substrate as donors and is catalyzed by sialidase in place of sialyltransferase. Thiem et a1.⁶ have reported the enzymatic synthesis of α(2→6)-linked sialyl galactose, glucose, lactose and lactosamine in preference to the corresponding α(2→3)-linked derivatives employing sialidase from vibrio cholerae, while Ajisaka et al.⁷ have synthesized α(2→3)-linked sialyl lactose and lactosamine with sialidase from new castle disease virus.

     

Quality control strategy for the determination of 210Po

A quality control programme is presented for the determination of ²¹⁰Po in samples from the phosphate ore-processing industry. Accuracy and precision of selected steps of the analytical procedure are quantified and the change in these parameters is monitored by analysis of hundreds of reference samples during the last two years.     

Temperature and variable strain rate sensitivity in recycled HDPE

The recycling of post-consumer plastics and their utilization as raw materials to develop value-added products has become an important goal worldwide. The present work is concerned with the thermo-mechanical analysis of recycled high-density polyethylene (HDPE) under uniaxial tensile loading. The main focus is to propose a one-dimensional phenomenological model able to describe the influence of temperature and strain rate on the mechanical behavior. Tensile tests were performed over a wide range of temperatures (from 25°C to 100°C). Each experiment was performed under controlled strain rate varying from 7.25 × 10⁻⁵ s⁻¹ to 7.25 × 10⁻³ s⁻¹ in steps. It is shown that only one tensile test performed at three different temperatures is necessary to fully identify experimentally all material parameters that arise in the theory. Thus, with this experimental procedure, the number of tests used to evaluate the mechanical properties of recycled HDPE is significantly reduced. The experiments are compared with the model predictions and show good agreement.     

An efficient combined procedure for the extreme trace analysis of gold, platinum, palladium and rhodium with the aid of graphite furnace atomic absorption spectrometry and total-reflection X-ray fluorescence analysis

Summary The determination of Au, Pt, Pd and Rh at ng- and pg-levels in manganese crust, natural water and geological and biological standards is based upon extraction of these elements with Se via a coprecipitation technique, elaborated as a micro-technique. All steps of the combined procedure are controlled by radiotracer (¹⁹⁵Au) and yields vary between 90 and 100%. Zeeman graphite furnace atomic absorption spectrometry and total reflection X-ray spectrometry are employed as determination steps. Sources of systematic errors are discussed.

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Leistungsfähiges Kombinationsverfahren zur Ultraspurenanalyse von Au, Pt, Pd und Rh mit Hilfe der GF-AAS und der Totalreflexions-Röntgenfluorescenzanalyse

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Dedicated to Prof. Dr. F. Huber on the occasion of his 60th birthday     

Isolation and analysis of polycyclic aromatic hydrocarbons from natural water using accelerated solvent extraction followed by gas chromatography-mass spectrometry

An innovative analytical procedure for the analysis of polycyclic aromatic hydrocarbons (PAHs) from large-volume water samples is presented. It involves sample preparation, sampling and the elution process in an automated continuous procedure involving the ASE technique. Prior to sampling, a XAD-2 resin column is prepared on the basis of a commercial accelerated solvent extraction (ASE) cartridge so that the resin bed is permanently fixed. Then, the XAD column inside the ASE cartridge is cleaned and conditioned. The sampling procedure involves conventional filtration with subsequent isolation of dissolved PAHs on an XAD-2 resin contained in the ASE cartridge. After sampling, the XAD-2 resin content inside the cartridge is eluted by ASE without any further sample preparation and subsequently reused. In order to validate the procedure, the PAHs were isolated from water samples from the Lake Maggiore (North of Italy) using both XAD-2 resin adsorption and hexane liquid-liquid extraction according to the International Standard Methodology ISO 17993. The mean percentages of deviation between concentrations obtained by both methodologies range from 6% for benzo(a)pyrene to 15% for fluoranthene and benzo(b,k)fluoranthene. Compared to the traditional techniques, this procedure offers numerous practical advantages: easy to perform, fast, savings in solvent volume and in time, all steps are fully automated thus avoiding any XAD-2 resin manipulation during and between steps and moreover, low detection limits were provided (0.001 ng l⁻¹ for chrysene, benzo(b,k)fluoranthene, benzo(a)pyrene, dibenz(a,h)anthracene, benzo(g,h,i)perylene and indeno(1,2,3-cd)pyrene, and 0.01 ng l⁻¹ for acenaphthylene and fluoranthene).This procedure was developed in the frame of a project aimed at evaluating the diffuse input of organic contaminants in the Lake Maggiore.