Ng Pd Research Articles

The metallobiochemistry of ultratrace levels of platinum group elements in the rat.

The use of platinum, palladium and rhodium (Platinum Group Elements - PGEs) and the possibility of exposure to their ultratrace levels is increasing. In fact, the exponential development of metallic PGE-based nanoparticles (<100 nm in size) opens extraordinary perspectives in the areas of electrocatalysts and catalytic converters, magnetic nanopowders, polymer membranes, cancer therapy, coatings, plastics, nanofibres and textiles. Like other metal-based nanoparticles, exposure to PGEs nanoparticles may result in a release of ultratrace amounts of Pt, Pd, Rh ions in the body whose metabolic fate and toxicity still need to be evaluated. Furthermore, PGEs can act as allergic sensitizers by acting as haptens and inducing both type I and IV allergic reactions. In this work we studied the in vivo metabolic patterns of ultratrace levels of potent allergens and sensitizers PGE halogenated salts. (191)Pt, (103)Pd and (101m)Rh radioisotopes were prepared via cyclotron irradiation and used for radiolabelling Na2(191)PtCl4, Na2(103)PdCl4 and Na2(101m)RhCl6 salts. These anionic chlorocomplexes were intraperitoneally injected into rats (114 ng Pt kg(-1) bodyweight; 24 ng Pd kg(-1) b.w.; 16 ng Rh kg(-1) b.w.). At 16 h post-exposure, PGEs were poorly but significantly retained in all tissues analysed. Kidneys, spleen, adrenal gland, liver, pancreas and small intestine were the organs with the highest Pt, Pd, Rh concentrations. In the blood 30-35% of (103)Pd and (191)Pt and 10% of (101m)Rh were recovered in the plasma, mainly bound to albumin and to a less extent to transferrin. The hepatic and renal intracellular distribution showed the highest recovery of (191)Pt, (103)Pd and (101m)Rh in the nuclear fraction (liver) and in the cytosol (kidney). Chromatographic separation and ultrafiltration experiments on kidney and liver cytosols showed the strong ability of biochemical macromolecules to bind (191)Pt, (103)Pd and (101m)Rh, and being responsible for the retention of the three elements in the body. The link to macromolecules is the basis for the sensitizing capacity of PGEs.

Simultaneous determination of Co, Fe, Ni and Pb in carbon nanotubes by means of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry

This work explores the possibilities of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry for the direct analysis of carbon nanotubes. In particular, the simultaneous determination of Co, Fe, Ni and Pb is intended, as these elements are typically found in these samples as impurities. The results demonstrate that it is possible to find spectral (monitoring of the region between 283.168 and 283.481 nm), furnace (2500 °C for atomization; use of 100 ng Pd as a chemical modifier) and detector (use of side pixels to expand the linear range) conditions that permit the development of a fast and straightforward method for the simultaneous determination of the target elements at the levels at which they are typically found (mg g−1 for Co, Fe and Ni; μg g−1 for Pb) in carbon nanotubes. Limits of detection of 23 pg (Pb), 6 ng (Fe), 65 ng (Ni) and 86 ng (Co) were obtained, which are suitable for this type of sample. In this way, it was feasible to carry out the analysis of the samples investigated (one candidate reference material and three commercially available samples) and achieve accurate results when constructing the calibration curve with aqueous standards. Precision values for 5 solid sample replicates varied between 7 and 15% RSD in most cases. Overall, the proposed method shows important benefits for the cost-effective analysis of such complex samples in routine labs.

Determination of toxic trace impurities in titanium dioxide by solid sampling-electrothermal vaporization-inductively coupled plasma mass spectrometry

This paper reports on the performance of solid sampling-electrothermal vaporization-inductively coupled plasma mass spectrometry (SS-ETV-ICPMS) for the direct multi-element determination of six toxic trace impurities (As, Cd, Hg, Pb, Sb and Zn) in three different TiO2 samples. Careful selection of the most suitable target nuclides for the different analytes and temperature program optimization permit the reliable monitoring of the analytes of interest, while avoiding the occurrence of potentially relevant spectral interferences. A pyrolysis-free program, in which simultaneous vaporization of all the analytes is carried out at a relatively low temperature (1700 °C), was used. In this way, sample matrix and analyte co-vaporization is avoided, considerably reducing matrix effects and allowing the determination of Zn, which would otherwise be hampered by a spectral overlap with TiO+ ions. Calibration against aqueous standards was found to be feasible. Addition of 50 ng Pd as carrier agent improved the linearity of the calibration curves. Two different internal standards (105Pd+ and 125Te+) were used to compensate for matrix effects. The method thus developed exhibits interesting features: low limits of detection (ng g−1 range) for all of the elements, at least an order of magnitude lower than those for digestion-based procedures; high sample throughput (maximum 35 min per determination), contrasting with the 2 h required for sample digestion and subsequent analysis; low sample consumption (a few milligrams only); precision values usually in the 9–13% RSD range; and last but not least, the absence of any sample pre-treatment, with the subsequent lower risk of analyte losses, contamination or personal and instrumental harms derived from the necessity of using hazardous reagents for sample digestion. SS-ETV-ICPMS therefore seems to be a promising alternative for industrial control analysis of TiO2 samples with analyte contents ranging from a few ng g−1 to several hundreds of µg g−1.

Theoretical prediction of noble-gas compounds: Ng–Pd–Ng and Ng–Pt–Ng

Following our recent study on Ng-Pt-Ng (Ng=Ar,Kr,Xe) [J. Chem. Phys. 123, 204321 (2005)], the binding of noble-gas atoms with Pd atom has been investigated by the ab initio coupled cluster CCSD(T) method with counterpoise corrections, including relativistic effects. It is shown that two Ng atoms bind with Pd atom in linear geometry due to the s-d(sigma) hybridization in Pd where the second Ng atom attaches with much larger binding energy than the first. The binding energies are evaluated as 4.0, 10.2, and 21.5 kcalmol for Ar-Pd-Ar, Kr-Pd-Kr, and Xe-Pd-Xe, respectively, relative to the dissociation limit, Pd ((1)S)+2Ng. In the hybrid Ng complexes, the binding energies for XePd and Ng (=Ar,Kr) are evaluated as 4.0 and 6.9 kcalmol for XePd-Ar and XePd-Kr, respectively. The fundamental frequencies and low-lying vibrational-rotational energy levels are determined for each compound by the variational method, based on the three-dimensional near-equilibrium potential energy surface. Results of vibrational-rotational analyses for Ng-Pt-Ng (Ng=Ar,Kr,Xe) and Xe-Pt-Ng (Ng=He,Ne,Ar,Kr) compounds are also given.

Angiotensin II and III microinjections into the zona incerta influence drinking behavior

Different doses of angiotensin II (AII) or angiotensin III (AIII) microinjections into the zona incerta have been studied on drinking of rats in separate experiments during the consequent 60-min-daily-drinking period. Also, the dipsogen power of only the effective dose of AII and AIII was compared to vehicle treated rats. After, angiotensin receptor (AT 1, AT 2) antagonists on AII or AIII induced drinking were tested. In the first and second experiments only the 100 ng AII and the 200 ng AIII increased water intake significantly. In the third experiment the AII started its dipsogen effect earlier, at the 5 min measuring time, compared to the AIII. Both effects kept on lasting parallel from the 10 min on. Considering the antagonist pre-treatments in the fourth experiment, animals were injected with 90 ng losartan, an AT 1 antagonist, 180 ng PD 123319 or 200 ng CGP 42112, both AT 2 antagonists, respectively. Both AII and AIII increased water consumption. The effect of AII could be blocked by losartan, but not by PD 123319 or CGP 42112. On the other hand, the effect of AIII could not be blocked by losartan, but by both the PD 123319 and CGP 42112. Since, the effects of AII, AIII and angiotensin antagonists have not been tested in the zona incerta, the finding that water intake increased after AII or AIII injections and it could be blocked only by either of the antagonists suggests that AT 1 and AT 2 receptors play partially different roles in the regulation of water intake.

Investigations on the use of chemical modifiers for the direct determination of trace impurities in Al2O3 ceramic powders by slurry electrothermal evaporation coupled with inductively-coupled plasma mass spectrometry (ETV-ICP-MS).

The direct determination of trace impurities in Al2O3 ceramic basic powders by ICP-MS using electrothermal evaporation (ETV) with slurry sampling has been investigated. To increase interference-free analyte volatilization, the use of the palladium-group modifiers (PGM) IrCl3, Pd(NO3)2, and PdCl2 for the determination of Ca, Fe, Ga, Mg, Mn, Na, Ni, and V in Al2O3 powders was studied. Their role, which in ETV-ICP-MS and ETV-ICP-OES is to stabilize the investigated analyte during the ashing phase, to increase vaporization of the matrix, and to reduce transport losses was investigated. Optimum analysis results were obtained with PdCl2 modifier when 500 ng Pd was used for a sample weight of 100 microg Al2O3 injected into the ETV. Calibration was performed by standard addition with aqueous solutions of the analytes. The RSDs calculated from triplicate analysis ranged form 5 to 10%. Detection limits between 0.07 microg g(-1) (Ga) and 1.1 microg g(-1) (Na) were achieved. The accuracy was proven for the elements Ca, Fe, Ga, Mg, Mn, Na, Ni, and V by analyzing an NIST standard reference Al2O3 material (SRM 699) with a middle grain size of 16.4 microm. The analytical method was used for the analysis of Al2O3 powder (AKP 30, Sumitomo, Japan) with impurities in the low microg g(-1) range and a middle grain size of 1.1 microm. The results obtained for the elements Ca, Fe, Ga, Mg, Mn, Na, Ni, and V were comparable with those obtained by ICP-MS subsequent to conventional decomposition with hydrochloric acid at high pressure.

Room temperature phosphorescence of palladium(II) — coproporphyrin III complex in a precipitated nonionic surfactant micelle phase: determination of traces of palladium(II)

The palladium(II)—coproporphyrin III complex was distributed and concentrated in the surfactant phase precipitated from a homogeneous micellar solution of Triton X-100 by heating for 20 to 30 min at a temperature above its cloud point. This concentrated complex had strong phosphorescence at room temperature. Based on these findings, the room temperature phosphorimetric determination of 10 −9 M levels of Pd(II) was developed. The detection limit (signal-to-noise ratio = 3) was 2 × 10 −9 M (2.7 ng Pd 2+/15 ml), and the relative standard deviation was 2.1% for 1 × 10 −6 M (1.6 μg Pd 2+/15 ml) (6 determinations).

The stimulation of cholecystokinin receptors in the rostral nucleus accumbens significantly antagonizes the EEG and behavioural effects induced by phencyclidine in rats.

The influence of cholecystokinin (CCK), bilaterally injected into the rostral nucleus accumbens, on the EEG and behavioural effects induced by phencyclidine (PCP) has been studied in rats. CCK (10 ng) significantly inhibited PCP-induced EEG effects (increase of spectral power with respect to pre-drug tracing; increase of relative power distribution in the slowest frequency bands), and behavioural effects (circling and ataxia). The inhibitory effects of CCK were completely antagonized by 1 ng PD 135-158, a selective CCKB receptor antagonist, but not by lorglumide (1 microgram), a selective CCKA receptor antagonist. Since the effects induced by PCP in rodents have been proposed to be an experimental correlate of the psychotic symptoms it induces in humans, these results indicate that CCK may act as a neuroleptic. They also suggest that CCKB receptors located in the rostral nucleus accumbens may be involved in the neuroleptic-like activity of CCK.

The determination of palladium in fosinopril sodium (monopril) by ICP-MS

A rapid, sensitive ICP-MS method was developed to determine palladium in fosinopril sodium. The assay could not be carried out in a purely aqueous solvent owing to the instability of the palladium species in this media. It was found that the most appropriate vehcile for solubilization of this material was a solution of 25% (v/v) 2-butoxyethanol and water. A minimum quantifiable limit of 0.1 μm g −1 for Pd in the sample (corresponding to 1 ng Pd mL −1 in the analyte solution) was obtained.

Medium-pressure liquid chromatography of platinum metal ions on Spheron DEAE

Spheron DEAE (modified macroreticular hydroxyethylmethacrylate-ethylenedimethacrylate copolymer) was used for chromatographic separation and determination of Rh(III), Pd(II), and Pt(IV) in chloride medium. The most suitable composition of the mobile phase was looked for by studying the influence of hydrochloric acid concentration on the capacity ratios of the metal ions mentioned and on their resolution, as well as the influence of different additions to the mobile phase on the decrease of the high Pt(IV) retention. Using the photometric (UV) detection, the linear dependence was found up to following concentrations: Rh 200 mg l-1, Pd 2 g l-1, Pt 500 mg l-1. The detection limit was 23 ng Rh, 62 ng Pd and 96 ng Pt in 7 μl sample injected.The reproducibility of the determination was (as relative standard deviation for n = 3) 1-4%, relative error 0.7-7%.