Evaluation of measurement uncertainties for the determination of total metal content in soils by atomic absorption spectrometry

In this work estimation of measurement uncertainties associated with the total metal content in soils was done by an intralaboratory approach based on method validation and quality control data, and using two certified reference materials (CRM). CRM and soil samples were analyzed following procedures based on the methods that are applied to silicate materials. All elements were determined by atomic absorption spectrometry following a quality assurance program previously established. Quality control actions were implemented in order to provide reliable data. The precision under within-laboratory reproducibility conditions was estimated from triplicate analysis. The trueness component was determined as recovery of the analyte from CRMs: soil sample, SO-2 and river clay sediment, LGC 6139. Combined measurement uncertainty was expressed in terms of precision and recovery uncertainties and the later further split on CRM replicate analysis and uncertainty of the certified value components. The results obtained are critically discussed on the basis of the different contributions. For the selection of the reference material, the CRM dependent terms are critically compared in order to fulfill specific requirements. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mechanism of Ru(III) catalysis in acid bromate oxidation of 2-methylcyclohexanol

Kinetic investigations on Ru(III) catalyzed oxidation of 2-methylcyclohexanol by acidic solution of potassium bromate has been made in the presence of mercuric acetate as scavenger for bromide ions. A transient complex, formed between Ru(III) species and 2-methylcyclohexanol in 11 ratio, disproportionates in a slow and rate-controlling step to give the corresponding ketone and ruthenium(III) hydride, which, on interaction with acid bromate in a fast step regenerates catalytic species of Ru(III) for the recycling.

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2- , Ru(III) - . , Ru(III) 2- 11, (, ), (III). , Ru(III) .

     

Rapid determination of 90Sr/90Y in water samples by liquid scintillation and Cherenkov counting

Strontium-90 (⁹⁰Sr) is a ubiquitous contaminant at nuclear facilities, found at high concentrations in spent nuclear fuel and radioactive waste. Due to its long half-life and ability to be transported in groundwater, an accurate method for measuring ⁹⁰Sr in water samples is critical to the monitoring program of any nuclear facility. To address this need, a rapid procedure for sequential separation of Sr/Y was developed and tested in groundwater samples collected from an area of riverbed affected by a ⁹⁰Sr groundwater plume. Sixteen samples, plus spike and water blanks, were analyzed. Five different measurements were performed to determine the ⁹⁰Sr and yttrium-90 (⁹⁰Y) activities in the samples: direct triple-to-double-coincidence ratio (TDCR) Cherenkov counting of ⁹⁰Y, liquid scintillation (LS) counting for ⁹⁰Sr following radiochemical separation, LS counting for ⁹⁰Y following radiochemical separation, Cherenkov counting for ⁹⁰Y following radiochemical separation and LS counting of the Sr samples for ⁹⁰Y in-growth. The counting was done using a low-level Hidex 300SL TDCR counter. Each measurement method was compared for accuracy, sensitivity and efficiency. The results following Cherenkov counting and radiochemical separation were in very good agreement with one another.     

Rim,Side Arms,and Cavity: Three Sites for the Recognition of Anions by Tetraazolium Resorcinarene Cavitands

Two tetrabenzoimidazolium‐resorcinarene cavitands were prepared and used for the recognition of chloride, bromide, iodide, cyanide, nitrate, perchlorate, hexanoate, benzenesulfonate, and p‐toluenesulfonate. Binding affinities of the two cavitands were determined by ¹H NMR titration and computational analysis. The observed spectral changes were related to specific interaction sites, which were supported by the computational studies. In the case of the C2?H tetrabenzoimidazolium‐resorcinarene, the recognition region of the inorganic anions and hexanoate was located at the rim of the cavitand, although chloride and bromide also interacted with the aromatic C?H bonds located between adjacent arms of the cavitand. By contrast, the recognition of the two anions with an aromatic ring (benzenesulfonate and p‐toluenesulfonate) results from encapsulation of the aromatic part of the anions inside the hydrophobic cavity of the host. In the case of the C2?Me tetrabenzoimizazolium‐resorcinarene receptor, the ability of the molecule to bind all inorganic anions and hexanoate was suppressed, but the receptor maintained its ability to strongly bind benzenesulfonate and p‐toluenesulfonate. This is interpreted in terms of suppression of the ability of the cavitand to form hydrogen bonds at the rim of the molecule due to replacement of the C2?H proton by a methyl group, while the hydrophobic pocket of the molecule maintains its binding abilities.     

On the mechanisms of silicon atom abstraction reactions

A set of experiment were designed to verify that recoil ³¹Si atoms abstracts H and F atoms via a stepwise mechanism instead of a simulatenous mechanism to give silylenes suh as ³¹SiH₂, ³¹SiHF and ³¹SiF₂. In addition, a novel compound 1-flourosilacyclopent-3-ene, was synthesized     

Some observations of various 1,8 naphthoquino-dimethane biradicals by electron spin resonance spectroscopy

Photolysis of 8-methyl-1-naphthyldiazomethane at 4 K gives the triplet ESR spectrum of 1,8-naphthoquinodimethane but not that of 8-methyl-1-naphthylcarbene. Photolysis of either 8-methyl-1-azido-naphthalene or 8-amino-1-azidonaththalene does produce the triplet biradical spectra of 8-imino-1-naphthoquinomethane and 1,8-diiminonaphthoquinodimethane, in addition to the triplet nitrene spectra of 8-methyl-1-nitreno-naphthalene and 8-amino-1-nitreno-naphthalene. Curie Law analyses demonstrate that these biradicals are all ground state triplets. Hückel and INDO calculations pertaining to the biradicals are reported. Large charge transfer interactions were observed in the ESR spectra of 8 substituted-1-naphthyl nitrenes.     

Phenolic Characterization and Neuroprotective Properties of Grape Pomace Extracts

Vitis vinifera (grape) contains various compounds with acknowledged phytochemical and pharmacological properties. Among the different parts of the plant, pomace is of particular interest as a winemaking industry by-product. A characterization of the water extract from grape pomace from Montepulciano d’Abruzzo variety (Villamagna doc) was conducted, and the bioactive phenolic compounds were quantified through HPLC-DAD-MS analysis. HypoE22, a hypothalamic cell line, was challenged with an oxidative stimulus and exposed to different concentrations (1 µg/mL⁻¹ mg/mL) of the pomace extract for 24, 48, and 72 h. In the same conditions, cells were exposed to the sole catechin, in a concentration range (5–500 ng/mL) consistent with the catechin level in the extract. Cell proliferation was investigated by MTT assay, dopamine release through HPLC-EC method, PGE₂ amount by an ELISA kit, and expressions of neurotrophin brain-derived neurotrophic factor (BDNF) and of cyclooxygenase-2 (COX-2) by RT-PCR. The extract reverted the cytotoxicity exerted by the oxidative stimulus at all the experimental times in a dose-dependent manner, whereas the catechin was able to revert the oxidative stress-induced depletion of dopamine 48 h and 72 h after the stimulus. The extract and the catechin were also effective in preventing the downregulation of BDNF and the concomitant upregulation of COX-2 gene expression. In accordance, PGE₂ release was augmented by the oxidative stress conditions and reverted by the administration of the water extract from grace pomace and catechin, which were equally effective. These results suggest that the neuroprotection induced by the extract could be ascribed, albeit partially, to its catechin content.     

Synthesis of soluble polymers for medicine that degrade by intramolecular acid catalysis

Aqueous soluble polymers designed to rapidly degrade by an intramolecular assisted acid catalysed mechanism were prepared. Degradation studies at pH 5.5 and 2.0 exhibited a rapid first phase followed by a slower phase and incomplete degradation to macromonomeric species. The fast phase was attributed to repeat units containing a carboxylic acid pendent chain cis to an amide bond in the polymer mainchain and the slow phase by the absence of this free carboxylic acid moiety.     

Two dimensional infrared (2D-IR) spectroscopic studies of the viscoelastic behavior of liquid crystalline polyurethanes

Dynamic infrared dichroism techniques have been used to study a complex side chain liquid crystalline segmented polyurethane. The obtained dynamic spectra were analyzed using two dimensional infrared techniques (2D-IR) that allow the easier interperation of the dynamic response of this system. Side chain mesogens are monitored by the cyano tag at the end of the molecule while the hard segments can be viewed in the carbonyl spectral region. A study of the different parts of the macromolecule leads to an understanding of the elastic and the viscous orientation behavior of the polymer. We find that the elastic component of the strain aligns smectic layers parallel and hard domains perpendicular to the direction of strain. The viscous strain component, on the other hand, induces a perpendicular smectic layer and parallel hard domain orientation behavior. These observations are consistent with a model proposed in earlier work that the hard segments and the smectic layers change orientation as the applied strain is increased from low to high strains. In addition, we show further evidence for the coupling of the mechanical deformation behavior of the smectic layers and the hard domains and identified two primary relaxation times in this system.