Tungsten Rhodium Research Articles

Avaliação da qualidade da imagem e da Dose Glandular Média em Mamografia Digital.

The most important reference for breast cancer diagnosis is still the mammography. Mammographic technology has evolved in such a way that we have digital systems nowadays. Thus, image generation quality control must evolve as well. In this work, we have evaluated digital image quality and entrance skin dose (ESD) for different breast thicknesses simulated by PMMA plates (one, two, three and four centimeters) for different target filter combinations, suggesting a protocol optimization to the mammographic automatic system.We have used CDMAM 3.4 phantom (a contrast detail phantom) and its software in order to analyze digital images from a Siemens Mammomat Inspiration mammographic equipment. It has been used three combinations of target-filter: Molybdenum Molybdenum, Molybdenum Rhodium, Tungsten Rhodium. Different peak tensions were tested to each configuration: 24 kVp, 26 kVp, 28 kVp and 30 kVp. Altogether 52 different configurations were tested. In order to measure ESD, we used Radcal’s 10x5–6M ionization chamber.Results show that automatic configuration does not offer an optimized process. Tungsten Rhodium was the best option for all breast thicknesses, once it offered the best relation between image quality and mean glandular dose. This result differs from literature which states that the Molybdenum Molybdenum combination is the best option for thin breasts.

Flow injection on-line solid phase extraction for ultra-trace lead determination with hydride generation electrothermal atomic absorption spectrometry

The efficiencies of two types of chelating resins were evaluated and optimized for the extraction and determination of lead by flow injection graphite furnace and hydride generation atomic absorption spectrometry (FI-HG-ETAAS) in environmental water samples. The optimum analytical conditions were examined and the analytical features of each method were revealed and compared in terms of sensitivity, selectivity and accuracy. Lead determination by FI-HG-ETAAS using [1,5-bis(2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide immobilised on aminopropyl-controlled pore glass (PSTH-cpg, 55 nm) provides a detection limit of 3.0 ng l−1 lead with a relative standard deviation (R.S.D.) of 2.5% at the 50 ng l−1 level (n = 10) compared to silica gel funtionalized with methylthiosalicylate (TS-gel) which provides a detection limit of 82 ng l−1. Under the optimal experimental conditions, with the use of PSTH-cpg and a tungsten–rhodium coated graphite furnace, an enhancement factor of 20 was obtained with a sample consumption of 6.4 ml, while an enhancement factor of 3.5 was obtained with the use of TS-gel. Both methods have been applied to the determination of low levels of lead in environmental water samples. The results obtained show good agreement with certified or expected values.

Flow system with in-line separation/preconcentration coupled to graphite furnace atomic absorption spectrometry with W–Rh permanent modifier for copper determination in seawater

A flow system was coupled to a graphite furnace with a platform coated with tungsten–rhodium permanent chemical modifier for in-line separation and preconcentration of copper by employing a minicolumn loaded with 1-(2-tiazolylazo)-2-naphthol (TAN) immobilized on C 18-bonded silica fixed in the tip of the autosampler arm. Elution was made by sampling 35 μl of 0.50 mol l −1 HCl with further delivering into a coated platform. Remarkable improvements in both selectivity and sensitivity were observed. Copper(II) was effectively separated from solutions containing up to 20 g l −1 Na +; 10 g l −1 K +, Ca 2+ and Mg 2+; 1.0 g l −1 Fe 3+ and Zn 2+. For a sample flowing at 3.0 ml min −1 and a loading of 60 s, the detection limit was estimated as 5 ng l −1 Cu(II) at the 99.7% confidence level, and an enrichment factor of 33 was calculated. Coefficient of variation was estimated as 4% for a 0.30 μg l −1 copper solution ( n=20). The W–Rh permanent chemical modifier was used to improve system stability, analytical performance and atomizer lifetime. More than 1500 firings were carried out with the same atomizer without significant variations in sensitivity and precision. On account of the reagent immobilization, its consumption was lower than 0.2 μg per determination. In addition, TAN purification was unnecessary.

Copper determination in biological materials by ETAAS using W–Rh permanent modifier

A tungsten–rhodium treatment on the integrated platform of a transversely heated graphite atomiser was used as a permanent chemical modifier for the determination of copper in biological materials by using digested samples as well as slurry sampling in electrothermal atomic absorption spectrometry. The W–Rh permanent modifier was as efficient as Pd+Mg(NO 3) 2 conventional modifier for obtaining good Cu thermal stabilisation in the digested and slurry samples. The permanent W–Rh modifier remained stable by approximately 300 and 250 firings when 20 μl of digested sample and 20 μl of slurry were delivered into the atomiser, respectively. In addition, the permanent modifier increased the tube lifetime up to 1370 and 744 analytical measurements in the digested and slurry samples, respectively. Also, when the W–Rh permanent modifier was employed, there was less variation of the slope of the analytical curves during the total atomiser lifetime, resulting in a decreased need of re-calibration during routine analysis, increasing the sample throughput, and consequently diminishing the variable analytical costs. Detection limits obtained with W–Rh permanent modifier were 0.64 and 0.33 μg g −1 Cu for digested (dilution factor 100 ml g −1) and 1.0% m/v slurries of biological materials, respectively. Results for the determination of copper in the samples were in agreement with those obtained with decomposed sample solutions by using Pd+Mg(NO 3), since no statistical differences were found after applying the paired t-test at the 95% level.

The use of tungsten–rhodium permanent chemical modifier for cadmium determination in decomposed samples of biological materials and sediments by electrothermal atomic absorption spectrometry

A 250 μg W + 200 μg Rh coating (W–Rh) on the integrated platform of a transversely heated graphite atomiser (THGA) was used as a permanent chemical modifier for the determination of Cd in digests of biological materials and dissolved sediments by electrothermal atomic absorption spectrometry (ETAAS). The W–Rh permanent modifier was as efficient as NH 4H 2PO 4 + Mg(NO 3) 2 and Pd + Mg(NO 3) 2 conventional modifiers for obtaining good Cd thermal stabilisation in the decomposed samples. The permanent W–Rh modifier remained stable by approximately 300–350 firings when 20 μl of digested sample were delivered into the atomiser. In addition, the permanent modifier increased the tube lifetime up to 1450 analytical measurements in the decomposed samples containing 1.0% v/v HNO 3. Also, when the W–Rh permanent modifier was employed, there was less variation of the slope of the analytical curves during the total atomiser lifetime, resulting in a decreased need of recalibration during routine analysis, increasing the sample throughput, and consequently diminishing the variable analytical costs. The atomiser lifetime was limited to the THGA wall durability, because the W–Rh treated platform was intact after more than 1200 analytical firings. The W–Rh permanent modifier withstood acidic concentrations up to 5.0% v/v HNO 3 without changes in the coating lifetime as well as in the analytical signal. Detection limits obtained with W–Rh permanent modifier were 1.0 and 6 ng g −1 Cd for biological materials and sediments, which were 1.25 and 2.5 times better than NH 4H 2PO 4 + Mg(NO 3) 2 and Pd + Mg(NO 3) 2 mixtures, respectively. Results for the determination of cadmium in the samples were in agreement with those obtained with decomposed sample solutions by using NH 4H 2PO 4 + Mg(NO 3) 2 and Pd + Mg(NO 3), since no statistical differences were found after applying the paired t-test at the 99% level.

Tungsten–rhodium permanent chemical modifier for lead determination in sediment slurries by electrothermal atomic absorption spectrometry

Tungsten–rhodium permanent chemical modifier for lead determination in sediment slurries by electrothermal atomic absorption spectrometry

Evaluation of tungsten–rhodium coating on an integrated platform as a permanent chemical modifier for cadmium, lead, and selenium determination by electrothermal atomic absorption spectrometry

A tungsten–rhodium coating on the integrated platform of a transversely heated graphite atomizer is proposed as a permanent chemical modifier for the determination of Cd, Pb, and Se by electrothermal atomic absorption spectrometry. It was demonstrated that coating with 250μg W+200μg Rh is as efficient as the conventional Mg(NO3)2+NH4H2PO4 or Pd+Mg(NO3)2 modifiers for avoiding most serious interferences. The permanent W–Rh modifier remains stable for 300–350 firings of the furnace, and increases tube lifetime by 50%–100% when compared to pyrolytic carbon integrated platforms. Also, there is less degradation of sensitivity during the atomizer lifetime when compared with the conventional modifiers, resulting in a decreased need of re-calibration during routine analysis. The characteristic masses and detection limits achieved using the permanent modifier were respectively: Cd 1.1±0.4pg and 0.020μgL−1; Pb 30±3pg and 0.58μgL−1 and Se 42±5pg and 0.64μgL−1. Results from the determination of these elements in water reference materials were in agreement with the certified values, since no statistical differences were found by the paired t-test at the 95% level.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 94. Synthesis of di- and tri-metal compounds via the reagents [M(C–CCBut)(CO)2(η-C5H5)](M = Mo or W)

The alkynylmethylidynemetal compounds [M(C–CCBut)(CO)2(η-C5H5)](M = Mo or W) react with [Fe2(CO)9] in thf (tetrahydrofuran) at ambient temperatures to afford via alkylidyne group coupling the trimetal complexes [M2Fe{µ3-C2(CCBut)2}(CO)7(η-C5H5)2] in good yield. The reaction between the alkynylmethylidynetungsten reagent and [Fe2(CO)9] also gives small quantities of [Fe2{µ-ButC2CW(CO)2(η-C5H5)}(CO)6], a product in which a Fe2(CO)6 fragment is attached to the terminal CCBut group of the [W(C–CCBut)(CO)2(η-C5H5)] molecule. Treatment of [Mo(C–CCBut)(CO)2(η-C5H5)] in light petroleum with [Rh(CO)2(η5-C9H7)](C9H7= indenyl) affords a chromatographically separable mixture of the compounds [MoRh(µ-C–CCBut)(CO)3(η-C5H5)(η5-C9H7)], [Mo2Rh{µ3-C2(CCBut)2}(CO)4(η-C5H5)2(η5-C9H7)], and [MoRh2{µ3-C–CC-But}(µ-CO)(CO)2(η-C5H5)(η5-C9H7)2]. The corresponding tungsten–rhodium species [WRh(µ-C–CCBut)(CO)3(η-C5H5)(η5-C9H7)], and [WRh2{µ3-C–CCBut}(µ-CO)(CO)2(η-C5H5)(η5-C9H7)2] have also been prepared. The dimetal compound [MoRh(µ-C–CCBut)(CO)3(η-C5H5)(η5-C9H7)] reacts with [W(C–CCBut)(CO)2(η-C5H5)] to give the trimetal complex [MoWRh{µ3-C2(CCBut)2}(CO)4(η-C5H5)2(η5-C9H7)], while [WRh(µ-C–CCBut)(CO)3(η-C5H5)(η5-C9H7)] with [Fe2(CO)9] and [Co(η-C2H4)2(η-C5Me5)] affords, respectively, the compounds [WFeRh(µ3-C–CCBut)(µ-CO)(CO)5(η-C5H5)(η5-C9H7)] and [WCoRh(µ3-C–CCBut)(µ-CO)(CO)2(η-C5H5)(η-C5Me5)(η5-C9H7)]. The 1H and 13C-{1H} n.m.r. data for the new compounds are reported and discussed.

The synthesis and reactions of an anionic tungsten–carbyne complex stabilised by the carbaborane ligand 1,2-C2B9H9Me2; evidence for a novel cage hydroboration reaction

The salt [N(Ph3)2][W(CR)(CO)2(η5-1,2-C2B9H9Me2)](R = C6H4Me-4) reacts with the compounds [RhCl(PPh3)3], [Rh(PPh3)2(diene)][BF4](diene = cyclo-octa-1,5-diene or norbornadiene), and [AuCl(PPh3)] to give products with tungsten–rhodium or tungsten–gold bonds, the structures of which were determined by X-ray diffraction; that from the norbornadiene complex contains a nortricyclane moiety bonded to a boron atom of the C2B9 cage.