An improved method for technetium determination in environmental samples

Summary The recent developments of extraction chromatography and ICP-MS made easier the determination of ⁹⁹Tc in environmental samples. However, in the non-contaminated area, a pre-concentration procedure is necessary, because usually a large amount of sample is used for analysis. In this study, the ferrous ion (Fe²⁺) added as a reductant can make chemical yield from 50 to 80%, when larger than 100 liter water samples or 500 g soil samples are analyzed. The extraction chromatography with TEVA resin (EIChrom) and the measurement by ICP-MS have been developed using ^95mTc and ¹⁰³Ru as yield tracers. Detection limits of 3σ are 0.054 mBq/kg for 500 g soil and 0.032 µBq/lfor 500 l water. A pond named Hinotani, Mie Prefecture in the central part of Japan, was selected to be investigated as a natural system in a non-contaminated area. Surface soil near this pond, pond water and sediment were collected and analyzed for ⁹⁹Tc. In a high fall-out area, Okuetsu, Fukui Prefecture forest soil was collected and analyzed. The ⁹⁹Tc in the surface (0-5 cm) was 10.5±0.8 mBq/kg. The ⁹⁹Tc in Hinotani surface (0-5 cm) soil were 0.77±0.06 mBq/kg less than in Okuetsu. Technetium-99 has been determined in pond water, sediment (0-5 cm) and shrimps in the Hinotani pond, 0.25±0.02 mBq/l, 3.3±0.3 mBq/kg, 1.5±0.2 mBq/kg, respectively.     

An integrated coupled column liquid chromatography system for the determination of leukotriene metabolites in biological samples

Summary A fully integrated chromatographic system was developed for the determination of leukotrienes in biological samples using photodiode-array detection (PDAD), which eliminates time consuming manual sample handling steps. A special solid phase extraction, (SPE) methodology for leucotriene metabolite stability was developed which increased the recoveries and eliminates the contamination risk of biological samples. The inherent instability (autooxidation) of many of the leukotriene mediators, and the adsorption effects onto exposed surfaces in vials and in the chromatographic system were found to be very important parameters to control in order to circumvent high loss of sample analytes. By binding the cell supernatants to the functionalities of the SPE support stabilised these mediators. Cell culture samples were eluted through a disposable C₁₈ SPE column. The SPE columns were allowed to thaw and deposited in an automated sample handling unit (ASPEC XL). Desorption of the analytes was followed by a second on-line SPE step, to eliminate remaining interfering matrix compounds. Typical recoveries when stored at −70°C were in-between 55–97% except for (LTE₄) which was found to be around 40% after 72 days of storage. Seven reversed-phase packings were studied. Selectivity factors, as well as the separation efficiencies, were found to differ for the various C₁₈ bonded silica stationary phases. This integrated on-line column liquid chromatographic system was applied to the determination of leukotriene B₄, leukotriene C₄, leukotriene D₄, leukotriene and E₄ in human cell extracts using prostaglandin B₂ as the internal standard. More than 1500 biological samples were analysed. Some validation data are presented for unattended operations.     

An all-purpose injection system for gas chromatographic analyses of biological samples.

A versatile injection system for the direct introduction of samples into the gas chromatograph (GC) is described. Several years of experience in biological and pharmaceutical chemistry have led to the construction and final modification of this device. No modification of the injection port of the GC is necessary.     

Development of an on-line preconcentration system for zinc determination in biological samples

An on-line preconcentration system for zinc determination in 24-h urine, blood plasma and erythrocyte matrices by flame atomic absorption spectrometry (FAAS) was used. This procedure was based on adsorption of Zn(II) ions onto a minicolumn filled with silica gel, chemically modified with niobium(V) oxide (Nb₂O₅-SiO₂). The determination of the optimum conditions for Zn(II) preconcentration was done using two-level full factorial and Doehlert designs. In the optimization procedure, four variables (sample pH, eluent concentration, sample flow rate and eluent flow rate) were investigated. The results obtained from the full factorial design demonstrated that the sample pH and sample flow rate variables, and their interactions, were statistically significant. A Doehlert matrix was used in order to determine the optimum conditions for the sample pH and sample flow rate. The optimized conditions for sample pH and flow rate sampling were 6.6 and 7.1 ml min⁻¹, respectively, to obtain the maximum Zn(II) preconcentration and determination in the biological samples studied. Parameters of analytical curve, precision, effect of other ions in the proposed system and accuracy were achieved to assess the proposed method. The accuracy was confirmed by analysis of certified reference materials (urine Seronorm™ Trace Elements) and recovery tests in blood plasma and erythrocyte samples. Detection limit (3σ/S) of 0.77 μg l⁻¹, precision (calculated as relative standard deviation) of 1.5% for Zn(II) concentration of 10 μg l⁻¹ (n = 7) and a sampling frequency of 27 samples/h were obtained from the proposed system.     

An improved analytical method for the determination of urea nitrogen isotopomers in biological samples utilizing continuous flow isotope ratio mass spectrometry

Over the past few years numerous dual inlet isotope ratio mass spectrometry (IRMS) applications have been adapted to continuous flow systems which allow the automation of sample admission and a higher throughput. The isotopomer analysis of urea nitrogen by IRMS requires the offline conversion of urea into nitrogen gas before analysis. The oxidation of urea with LiOBr results in the monomolecular degradation of urea, which preserves the identity of the parent urea molecule, and has to be conducted under vacuum to prevent contamination with atmospheric nitrogen. We have developed an offline system of urea degradation utilizing disposable Exetainers, in which atmospheric nitrogen is displaced by helium. Recovery of urea nitrogen was linear within the range of the standards tested (0 to 420 microg nitrogen) and standard curves for 15N15N-urea standards showed high coefficients of determination (R2 > 0.9998). A small portion of urea degrades in a non-monomolecular fashion and has been shown to depend on the concentration of urea in the sample. Long-term storage of prepared samples showed a decline in 15N15N enrichment, suggesting air contamination. However, samples were stable for 24 h, which allows for the analysis of large sample batches. Interest in urea metabolism, particularly in ruminant species, has increased recently due to the environmental implications of urea and nitrogen excretion by farm animals. This novel analytical method will allow for accurate measurements and the rapid throughput needed in order to support these field studies.     

An improved method for the determination of uranium isotopes in environmental samples by alpha-spectrometry

In order to improve the selectivity of the uranium isotopes determination in environmental samples, further studies have been carried out, including (1) interference of ²¹⁰Po with uranium isotope determination, (2) distribution coefficients of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids, (3) decontamination factor of uranium from polonium of the recommended procedure, and (4) leaching effect comparison of two different leaching procedures in a lichen sample. Based on the new findings, a more accurate extraction chromatographic/ a-spectroscopy method has been developed. For the method's validation, four kinds of reference materials supplied by the IAEA have been tested. It is observed that nearly all the ²³⁸U, ²³⁴U and ²³⁵U concentrations obtained are in good agreement with the recommended or information values, showing that the method can give reliable results. A comparison with existing uranium determination methods has also been made. It is concluded that due to involving preconcentration and chemical separation, the extraction chromatographic/a-spectroscopy method is a more selective, very sensitive and accurate, and low cost method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectrophotometric flow injection methods for zinc determination in pharmaceutical and biological samples.

Zinc ions form a yellow complex with di-2-pyridyl ketone salicyloylhydrazone (DPKSH). This complex showed maximum absorption at 376 nm, and it was used to develop spectrophotometric flow injection methods for Zn(II) determination in different samples. Two types of flow systems were proposed. In the first system, a linear analytical curve was obtained in a concentration range from 0.217 to 4.60 mg L(-1) Zn(II), with a detection limit of 48.8 microg L(-1). In the second system, a minicolumn packed with an anion exchanger resin was used to concentrate Zn(II) as a chlorocomplex, and a linear analytical curve within a concentration range from 0.0824 to 2.06 mg L(-1) Zn(II) was obtained, having a detection limit of 13.9 microg L(-1). The developed methods were applied to biological and pharmaceutical samples, and a great compliance was observed by comparing the results with ones obtained by an atomic absorption technique.     

Methods for chromatographic determination of amanitins and related toxins in biological samples.

Methods for the chromatographic determination of amanitins, toxins of Amanita phalloides (Fr.), Link mushrooms and related toxins are reviewed; particular emphasis is given to high-performance liquid chromatographic methods. The main chemical and toxicological aspects are discussed, but the focus of the present review is on the analytical problems arising in a laboratory charged with the setting up of a procedure which can direct the appropriate clinical management of an intoxicated patient or solve a forensic case.     

An improved method for simultaneous analysis of steroid and phenolic endocrine disrupting chemicals in biological samples

An improved method was developed for the simultaneous determination of eight steroid and phenolic endocrine disrupting chemicals, such as oestrone (E1), 17β-oestradiol (E2), oestriol (E3), 17α-ethynylestradoil (EE2), 4-nonylphenol (4-NP), bisphenol A (BPA), 4-tert-octylphenol (4-t-OP) and 4-cumylphenol (4-CP), in biological samples. The optimal extraction and clean-up procedures were investigated using microwave-assisted extraction (MAE), automated gel permeation chromatography (GPC) and solid phase extraction (SPE). As a consequence, the most efficient extraction was achieved by using MAE with methanol as solvent at an extraction temperature of 110°C for 20?min. The clean-up of extracts was carried out by GPC on a Biobeads S-X3 column with cyclohexane/ethyl acetate (1:1, v/v) as mobile phase. Target compounds were eluted in the fraction from 7–14?min retention time. Moreover, the cleanest extracts were obtained by solid phase extraction with C-18 cartridges after the elution with 15?mL ethyl acetate. The final sample extracts were derivatised using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) (1% trimethylchlorosilane, TMCS) as derivatisation reagent with pyridine as the solvent. Quantification was performed by gas chromatography-mass spectrometry (GC-MS) with electron ionisation (EI) and selected ion monitoring (SIM) mode. The method was validated by spiked samples which showed good recovery and reproducibility. The overall recoveries ranged between 55.1% and 100.6%, with relative standard deviations (RSD) of 2.3–12.7% for the entire procedure. Method detection limits (MDL) ranged from 0.3 to 0.7?ng?g^?1 dry weight (dw). Performance of the method was demonstrated by its application on tissues from fish exposed to high concentration of EDCs in the laboratory. The developed method is a promising approach for the analysis of steroid and phenolic endocrine disrupting chemicals in various biological samples.     

An improved nephelometric method for the determination of small amounts of thiosulfate in aqueous samples

The procedure is based on decomposition of thiosulfate, with formation of sulfur, in the presence of 0.5 mol l^?1 nitric acid. Thiosulfate is determined in the range 15–100 mg l^?1, with a relative standard deviation of 5.4% and a mean relative error of 3.2%. These data are of the same order of magnitude as those obtained for the earlier silver/1,10-phenanthroline method. The present method has the advantage of being almost completely free from interferences; the only interference observed (sulfide) is easily eliminated.     

An improved method for the determination of the input applied to a linear system by deconvolution of the output. Application in thermokinetics

A simplified deconvolution procedure which can be used to remove the distortion, due to thermal lags, from calorimetric data is described and tested. The procedure is based on the state function theory. Noise in the deconvoluted data can be abated by smoothing the experimental data and by a careful choice of the data-sampling frequency. The method is adaptable to on-line processing by means of a microprocessor.

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Zusammenfassung Ein vereinfachtes Dekonvolutionsverfahren, das sich zur Behebung von infolge thermischer Lag-Erscheinungen auftretenden Zerrungen kalorimetrischer Daten eignet, wird beschrieben und getestet. Das Verfahren beruht auf der Theorie der Zustandsfunktion. Geräusche der Dekonvolutionsdaten können durch Ausgleichen der Versuchsdaten und durch sorgfältige Wahl der Datennahme-Frequenz gedämpft werden. Die Methode kann mittels eines Mikro-Verarbeiters zur on-line Verarbeitung eingesetzt werden.

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Résumé Une procédure simplifiée de déconvolution qui peut être utilisée pour éliminer des courbes calorimétriques, la distorsion causée par l'inertie thermique du calorimètre, est décrite et testée. La procédure est basée sur la théorie des variables d'état. Le bruit de fond des courbes corrigées peut être diminué par le lissage des données expérimentales et par le choix d'une fréquence d'échantillonnage appropriée. La méthode peut être adaptée au traitement en ligne des données au moyen d'un microprocesseur.

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The authors gratefully acknowledge the assistance of Dr. J. Van Bokhoven, Chemisch Laboratorium TNO, Rijswyk, the Netherlands, during the experimental part of this work.     

Gas chromatographic-mass spectrometric method for the determination of selenium in biological samples.

The determination of selenium by capillary gas chromatography-mass spectrometry (GC-MS), using an enriched stable isotope 76Se as internal standard, is described. Reference values for selenium in human biological fluids (serum, red blood cells and urine) are reported. With the advent of new compact capillary GC-MS (benchtop) instruments, this method will be very simple and accurate for routine analysis.     

An anion exchange method for the determination of241Am and plutonium in environmental and biological samples

Irradiation and post-irradiation losses in 7 crude oils encapsulated in polyethylene and irradiated in a flux of 10¹²n·cm⁻² sec⁻¹ have been thoroughly studied. The fraction of mercury released during irradiations ranging from 10 minutes to 2 hours is proportional to the integrated flux received by the samples and does not differ substantially from one oil to another. Post-irradiation loss rates at 20°C range between 0.017 and 0.027%·hr⁻¹. Storage at−20°C reduces them by at least a factor of 2. The influence on the activity of¹⁹⁷Hg due to losses in sample weight occuring during the post-irradiation period has been examined. The fraction of radiomercury retained inside the walls of the irradiation vials versus the irradiation time has been assessed. Contamination of an inner irradiation site following prolonged irradiations of oils containing 150 μg/g of this element has been evaluated and found to have a negligible impact for trace measurements above the ng/g level.     

An improved flow-injection system for spectrophotometric determination of molybdenum and tungsten in tool steels

A flow-injection procedure for simultaneous spectrophotometric determination of tungsten and molybdenum in steel alloys is proposed. The method exploits the catalytic effects of Mo(VI) and W(VI) on the rate of iodide oxidation by hydrogen peroxide under acidic conditions. A novel strategy for ion-exchange separation of the potential interfering species is proposed, and an AG50W-X8 cationic resin mini-column is used. The sample is injected twice, originating two sequential plugs, citrate being added to one of them in order to suppress the W(VI) catalytic activity thus providing the kinetic discrimination.The system handles 70 samples per hour and requires 1.6 mg KI per determination. A linear response is verified up to 10 mg l⁻¹ Mo (or W) in the injectate, and signal additivity is 98-103%. Results are precise (R.S.D. < 0.04) and in agreement with ICP-OES. Running a standard reference material (IPT-50) assessed also accuracy.