Determination of ultra-trace Pt, Pd and Rh in seawater using an off-line pre-concentration method and inductively coupled plasma mass spectrometry.

A method was modified for the preconcentration of platinum (Pt), palladium (Pd) and rhodium (Rh) from seawater by a solid phase extraction using a commercially available resin Nobias-chelate PA1®. All the determination was conducted using inductively coupled plasma mass spectrometry (ICP-MS) which had a low detection limit for Pt, Pd and Rh, about 16.53, 16.41 and 26.88 pg L-1, respectively. It was found that the adsorption performance of the resin was closely related to the matrix, ligands and pH of the samples. Significant difference in recovery was found in various samples: seawater ≈ artificial seawater > ultra-pure deionized water. This method had low method blank in the range of 5.51-8.89 pg L-1 and high enrichment factor of up to 180-200. The recoveries of Pt and Pd were 93 ±â€¯4.2% in the spiked real seawater. However, the recovery of Rh on the resin was below 70% but stable in the range of 65-68%. It indicated that the Rh recovery seemed to be reproducible and higher volumes of seawater must be processed in order to obtain the lower limit of quantification and excellent recovery.

Monitorización de la presencia y distribución de platino y rodio en suelos urbanos de Alcalá de Henares (Madrid, España) / Monitoring the presence and distribution of platinum and rhodium in urban soils of Alcala de Henares (Madrid, Spain)

El constante desarrollo urbanístico y demográfico ha conllevado la aparición de nuevos riesgos para la salud humana en el medioambiente urbano. En los últimos años, se ha observado un fuerte incremento de la presencia de metales y metaloides en suelos urbanos, incluido la presencia de metales poco estudiados como los elementos del grupo del platino (PGE): platino (Pt), paladio (Pd) y rodio (Rh). Dada la creciente preocupación sobre los efectos nocivos de estos nuevos contaminantes para la salud humana, se han determinado los niveles de estos metales en los suelos de distintas zonas de Alcalá de Henares (Madrid). La acumulación de Pt y Rh ha sido significativamente inferior a las observadas en suelos de otras ciudades del mundo. La zona industrial y el centro urbano de la ciudad contienen significativamente niveles más elevados de PGEs debido al mayor volumen de tráfico, el tipo de conducción de parada/arranque, la actividad industrial y la cercanía del hospital Príncipe de Asturias. No obstante, los niveles encontrados parecerían implicar un riesgo mínimo para la salud de la población alcalaína, aunque son necesarios más estudios. Así, se hace necesario el establecimiento de dosis de referencia oral e inhalatoria (RfDo y RfCi) para PGEs, con el fin de establecer protocolos para proteger la salud humana en el medio urbano

The constant urban and demographic development has led to the emergence of new risks to human health in the urban environment. In recent years, there has been a sharp increase in the presence of metals and metalloids in urban soils, including the presence of metals little studied as the elements of the platinum group (PGE): platinum (Pt), palladium (Pd) and rhodium (Rh). Given the growing concern about the harmful effects of these new pollutants to human health, have determined the levels of these metals in the soils of different areas of Alcalá de Henares (Madrid). The accumulation of Pt and Rh has been significantly lower than those observed in soils from other cities. The industrial area and the center of the city contain significantly higher levels of PGEs due to the higher volume of traffic, type of driving stop / start, industrial activity and the proximity of Prince of Asturias hospital. However, the levels found appear to involve minimal risk to the health of the population alcalaína, although more studies are needed. Thus, the establishment of dose oral and inhalation reference (RfDo and RFCI) for PGEs is necessary, in order to establish protocols to protect human health in urban areas. although more studies are needed. Thus, the establishment of dose oral and inhalation reference (RfDo and RFCI) for PGEs is necessary, in order to establish protocols to protect human health in urban areas. although more studies are needed. Thus, the establishment of dose oral and inhalation reference (RfDo and RFCI) for PGEs is necessary, in order to establish protocols to protect human health in urban areas

Separation and preconcentration of trace amounts of rhodium using a dispersive liquid-liquid microextraction method and its determination by flame atomic absorption spectrometry.

A sensitive and selective method for the determination of low levels of rhodium (Rh) in environmental samples is needed. In the proposed method, an extracting solvent with a lower toxicity and density than the other solvents typically used in dispersive liquid-liquid microextraction was used to extract trace amounts of Rh from aqueous samples. Rh ions were complexed with 1-(2-pyridylazo)-2-naphthol in the pH range of 3.2-4.7 and extracted with dispersive liquid-liquid microextraction. The type and volume of the extracting solvent and dispersive solvent, centrifugation time, pH, amount of the chelating agent, and sample ionic strength were carefully studied. Under the optimal conditions, the LOD and RSD were 0.36 ng/mL (3Sb/m, n = 7) and +/-2.0% (n = 7), respectively. The calibration curve was linear in the range of 4.0-800 ng/mL. The method was applied to the determination of Rh in well and tap water, and spiked recoveries were in the range of 96-103.7%.

Flame atomic absorption spectrometry for the determination of trace amount of rhodium after separation and preconcentration onto modified multiwalled carbon nanotubes as a new solid sorbent.

The present article reports on the application of modified multiwalled carbon nanotubes (MMWCNTs) as a new, easily prepared and stable solid sorbent for the preconcentration of trace rhodium ion in aqueous solution. Rhodium ions were complexed with 1-(2-pyridylazo)-2-naphthol (PAN) in the pH range of 3.2-4.7 and then the formed Rh-PAN complex was adsorbed on the oxidized MWCNTs. The adsorbed complex was eluted from MWCNTs sorbent with 5.0 mL of N,N-dimethylformamide (DMF). The rhodium in eluted solution was determined by flame atomic absorption spectrometry (FAAS). Linear range for the determination of rhodium was maintained between 0.16 ng mL(-1) and 25.0 microg mL(-1) in initial solution. Relative standard deviation for the 10 replicated determination of 4.0 microg mL(-1) of rhodium was +/-0.97%. Detection limit was 0.010 ng mL(-1) in initial solution (3S(bl), n=10) and preconcentration factor was 120. Sensitivity for 1% absorbance of rhodium (III) was 0.112 microg mL(-1). The sorption capacity of oxidized MWCNTs for Rh (III) was 6.6 mg g(-1). The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type, breakthrough volume and interference ions were studied for the preconcentration of Rh(3+). The proposed method was successfully applied to the extraction and determination of rhodium in different samples.

Liquid-liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions using tri-iso-octylamine.

Liquid-liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions was carried out using tri-iso-octylamine (Alamine 308) as an extractant diluted in kerosene. The percentage extraction of platinum(IV) and rhodium(III) increased with increase in acid concentration up to 8 mol L(-1). However, at 10 mol L(-1) HCl concentration, the extraction behavior was reversed, indicating the solvation type mechanism during extraction. The quantitative extraction of approximately 98% platinum(IV) and 36% rhodium(III) was achieved with 0.01 mol L(-1) Alamine 308. The highest separation factor (S.F.=184.7) of platinum(IV) and rhodium(III) was achieved with 0.01 mol L(-1) Alamine 308 at 1.0 mol L(-1) of hydrochloric acid concentration. Alkaline metal salts like sodium chloride, sodium nitrate, sodium thiocyanate, lithium chloride, lithium nitrate, potassium chloride and potassium thiocyanate used for the salting-out effect. LiCl proved as best salt for the extraction of platinum(IV). Temperature effect demonstrates that the extraction process is exothermic. Hydrochloric acid and thiourea mixture proved to be better stripping reagents when compared with other mineral acids and bases.

Recoil effect on beta-decaying in vivo generators, interpreted for (103)Pd/(103m)Rh.

The use of Auger emitters as potential radiopharmaceuticals is being increasingly investigated. One of the radionuclides of interest is (103m)Rh, which can be produced from (103)Ru or (103)Pd in an in vivo generator. A potential problem, however, is the recoil of the (103m)Rh out of the carrier molecule and even out of the target cell. In order to determine the likelihood of this happening in the (103)Pd/(103m)Rh, case calculations were made to prove that this does not happen. The equations were generalised for all radionuclides with an atomic mass of 10-240 as a tool for determining the recoil threshold of any beta-emitting radionuclide.

Recovery of rhodium(III) from solutions and industrial wastewaters by a sulfate-reducing bacteria consortium.

A quantitative analysis of the rate of removal of rhodium(III) by a resting sulfate-reducing bacteria (SRB) consortium under different initial rhodium and biomass concentrations, pH, temperature, and electron donor was studied. Rhodium speciation was found to be the main factor controlling the rate of its removal from solution. SRB cells were found to have a higher affinity for anionic rhodium species, as compared to both cationic and neutral species, which become abundant when speciation equilibrium was reached. Consequently, a pH-dependent rate of rhodium removal from solution was observed. The maximum SRB uptake capacity for rhodium was found to be 66 mg of rhodium per gram of resting SRB biomass. Electron microscopy studies revealed a time-dependent localization and distribution of rhodium precipitates, initially intracellularly and then extracellularly, suggesting the involvement of an enzymatic reductive precipitation process. When a purified hydrogenase enzyme was incubated with rhodium chloride solution under hydrogen, 88% of the rhodium was removed within 1 h, whereas with a soluble extract from SRB 77% was removed within 10 min. Due to the low pH of the industrial effluent (1.31), the enzymatic reduction of rhodium by the purified hydrogenase was greatly limited, and it was apparent that an industrial effluent pretreatment was necessary before the application of an enzymatic treatment. In the present study, however, it was established that SRB are good candidates for the enzymatic recovery of rhodium from both aqueous solution and industrial effluent.

Synthesis and efficiency of a spherical macroporous epoxy-polyamide chelating resin for preconcentrating and separating trace noble metal ions.

The determination of noble metals in various materials usually requires their preconcentration and separation from other elements. In spite of the improvements in analytical instrumentation and the development of new analytical techniques such as ICP-MS, which are capable of detecting metal ions at ppt levels, the interference caused by the sample matrix still exists and is perhaps the most serious problem, making a pre-determination enrichment step necessary. Thus, the search for efficient preconcentration and separation methods is essential. A series of chelating resins that can selectively adsorb noble metal ions from aqueous solutions have been described. Functional groups, such as salicylaldoxime and thiosemicarbazide have been incorporated in cross-linked polymers or porous silica gel. These resins have very high selectivity for one or several types of noble metal ion. However, desorption of noble metals from these resins is usually difficult. Hence, the development of an adsorbent from which noble metals can be easily desorbed is needed. In this paper, a new spherical macroporous epoxy-polyamide chelating resin that met this requirement was synthesized by one step reaction. The synthesis of the resin was safe, rapid and more simple and economical than many report adsorbents. Meanwhile, the resin showed more advantages: better acid and alkali resistance; higher adsorption capacity and lower preconcentration concentrations. A resin column procedure combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the determination of trace Rh(III), Ru(III) and Ir(IV) in real samples was established.

A novel electrobiotechnology for the recovery of precious metals from spent automotive catalysts.

Platinum group metals are routinely used in automotive catalysts but recycle technology lags behind demand. There is no available 'dean technology' and leach solutions (e.g. aqua regia) to solubilise the metals from scrap are highly aggressive. A microwave-assisted leaching method was developed which gave 80% metals recovery, with the leach time reduced from 2 h to 15 min using 50% (aq.) diluted aqua regia to give potentially a more biocompatible leachate. Desulfovibrio desulfuricans reduces soluble platinum group metals to cell-bound insoluble base metals (e.g. Pd(II) --> Pd(0)). For use, biofilm was immobilised on a Pd-23% Ag solid alloy membrane which delivered H. to the cells via an electrochemical chamber at the back-side. The biomass-coated Pd-Ag alloy electrode was used in a flow-through reactor for recovery of Pd, Pt and Rh from aqua regia leachates (pH 2.5) of spent automotive catalysts with up to 90% efficiency at a flow residence time of 15 minutes. Free cells did not reduce platinum group metals from the leachates but the electrobioreactor did so using biofilm-cells pre-loaded with Pd(0). Reactors lacking biomass or reactors with heat-killed biofilm removed less platinum group metals, via electrochemically-synthesised H. reductant alone. The use of an active biofilm layer in a flow-through electrobioreactor provides a simple, dean and rapid potential recycle technology.

How do MgATP analogues differentially modify high-affinity and low-affinity ATP binding sites of Na+/K(+)-ATPase?

The exchange-inert tetra-ammino-chromium complex of ATP [Cr(NH3)4ATP], unlike the analogous cobalt complex Co(NH3)4ATP, inactivated Na+/K(+)-ATPase slowly by interacting with the high-affinity ATP binding site. The inactivation proceeded at 37 degrees C with an inactivation rate constant of 1.34 x 10(-3) min-1 and with a dissociation constant of 0.62 microM. To assess the potential role of the water ligands of metal in binding and inactivation, a kinetic analysis of the inactivation of Na+/K(+)-ATPase by Cr(NH3)4ATP, and its H2O-substituted derivatives Cr(NH3)3(H2O)ATP, Cr(NH3)2(H2O)2ATP and Cr(H2O)4ATP was carried out. The substitution of the H2O ligands with NH3 ligands increased the apparent binding affinity and decreased the inactivation rate constants of the enzyme by these complexes. Inactivation by Cr(H2O)4ATP was 29-fold faster than the inactivation by Cr(NH3)4ATP. These results suggested that substitution to Cr(III) occurs during the inactivation of the enzyme. Additionally hydrogen bonding between water ligands of metal and the enzyme's active-site residues does not seem to play a significant role in the inactivation of Na+/K(+)-ATPase by Cr(III)-ATP complexes. Inactivation of the enzyme by Rh(H2O)nATP occurred by binding of this analogue to the high-affinity ATP site with an apparent dissociation constant of 1.8 microM. The observed inactivation rate constant of 2.11 x 10(-3) min-1 became higher when Na+ or Mg2+ or both were present. The presence of K+ however, increased the dissociation constant without altering the inactivation rate constant. High concentrations of Na+ reactivated the Rh(H2O)nATP-inactivated enzyme. Co(NH3)4ATP inactivates Na+/K(+)-ATPase by binding to the low-affinity ATP binding site only at high concentrations. However, inactivation of the enzyme by Cr(III)-ATP or Rh(III)-ATP complexes was prevented when low concentrations of Co(NH3)4ATP were present. This indicates that, although Co(NH3)4ATP interacts with both ATP sites, inactivation occurs only through the low-affinity ATP site. Inactivation of Na+/K(+)-ATPase was faster by the delta isomer of Co(NH3)4ATP than by the delta isomer. Co(NH3)4ATP, but not Cr(H2O)4ATP or adenosine 5'-[beta,gamma-methylene]triphosphate competitively inhibited K(+)-activated p-nitrophenylphosphatase activity of Na+/K(+)-ATPase, which is assumed to be a partial reaction of the enzyme catalyzed by the low-affinity ATP binding site.

105Rh as a potential radiotherapeutic agent.

The production of 35.5-h 105Rh (560- and 250-keV betas) by neutron activation of 104Ru followed by beta decay of 4.4-h 105Ru is discussed. A simple procedure for producing 105Rh in 10-100 mCi quantities at specific activities of 700-10,000 Ci/mmol is described.

[Separation of [Rh-103m]-rhodocene derivatives from the parent [103Ru]ruthenocene derivatives and their organ distribution]. / Abtrennung von [103mRh]Rhodocen-Derivaten von den analogen [103Ru]Ruthenocen-Derivaten und deren Organ-Verteilung.

The radioactive decay of [103Ru]ruthenocene derivatives leads to 103mRh labelled rhodocinium derivatives, which can be separated by the extraction of a lipophilic solution of the ruthenocen derivate with water. The separation factor 103mRh/103Ru reaches values of 32:1 Rh3+ ions are not liberated and extracted. The organ distribution of the 103mRh labelled rhodocinium derivatives gained from ruthenocene and from N-isopropyl-ruthenocene amphetamine is different from the distribution of the parent ruthenocene compound. The liver and kidney uptake of the rhodocinium-amphetamine is much higher than the uptake with ruthenocene amphetamine.