Christina Hein

Influence of metal loading and humic acid functional groups on the complexation behavior of trivalent lanthanides analyzed by CE-ICP-MS

The complexation behavior of Aldrich humic acid (AHA) and a modified humic acid (AHA-PB) with blocked phenolic hydroxyl groups for trivalent lanthanides (Ln) is compared, and their influence on the mobility of Ln(III) in an aquifer is analyzed. As speciation technique, capillary electrophoresis (CE) was hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). For metal loading experiments 25 mg L(-1) of AHA and different concentrations (cLn(Eu+Gd)=100-6000 μg L(-1)) of Eu(III) and Gd(III) in 10mM NaClO4 at pH 5 were applied. By CE-ICP-MS, three Ln-fractions, assumed to be uncomplexed, weakly and strongly AHA-complexed metal can be detected. For the used Ln/AHA-ratios conservative complex stability constants log βLnAHA decrease from 6.33 (100 μg L(-1) Ln(3+)) to 4.31 (6000 μg L(-1) Ln(3+)) with growing Ln-content. In order to verify the postulated weaker and stronger humic acid binding sites for trivalent Eu and Gd, a modified AHA with blocked functional groups was used. For these experiments 500 μg L(-1) Eu and 25 mg L(-1) AHA and AHA-PB in 10mM NaClO4 at pH-values ranging from 3 to 10 have been applied. With AHA-PB, where 84% of the phenolic OH-groups and 40% of the COOH-groups were blocked, Eu complexation was significantly lower, especially at the strong binding sites. The log β-values decrease from 6.11 (pH 10) to 5.61 at pH 3 (AHA) and for AHA-PB from 6.01 (pH 7) to 3.94 at pH 3. As a potential consequence, particularly humic acids with a high amount of strong binding sites (e.g. phenolic OH- and COOH-groups) can be responsible for a higher metal mobility in the aquifer due to the formation of dissolved negatively charged metal-humate species.

New approach of a transient ICP-MS measurement method for samples with high salinity

In the near future it is necessary to establish a disposal for high level nuclear waste (HLW) in deep and stable geological formations. In Germany typical host rocks are salt or claystone. Suitable clay formations exist in the south and in the north of Germany. The geochemical conditions of these clay formations show a strong difference. In the northern ionic strengths of the pore water up to 5M are observed. The determination of parameters like Kd values during sorption experiments of metal ions like uranium or europium as homologues for trivalent actinides onto clay stones are very important for long term safety analysis. The measurement of the low concentrated, not sorbed analytes commonly takes place by inductively coupled plasma mass spectrometry (ICP-MS). A direct measurement of high saline samples like seawater with more than 1% total dissolved salt content is not possible. Alternatives like sample clean up, preconcentration or strong dilution have more disadvantages than advantages for example more preparation steps or additional and expensive components. With a small modification of the ICP-MS sample introduction system and a home-made reprogramming of the autosampler a transient analysing method was developed which is suitable for measuring metal ions like europium and uranium in high saline sample matrices up to 5M (NaCl). Comparisons at low ionic strength between the default and the transient measurement show the latter performs similarly well to the default measurement. Additionally no time consuming sample clean-up or expensive online dilution or matrix removal systems are necessary and the analysation shows a high sensitivity due to the data processing based on the peak area.

Killing of bacteria by copper, cadmium, and silver surfaces reveals relevant physicochemical parameters

The killing of bacteria on metallic copper surfaces in minutes to hours is referred to as contact killing. Why copper possesses such strong antimicrobial activity has remained enigmatic. Based on the physicochemical properties of metals, it was recently predicted that cadmium should also be active in contact killing [Hans et al., Biointerphases 11, 018902 (2010)]. Here, the authors show that cadmium is indeed antimicrobial. It kills three logs of bacteria in 9 h, compared to copper which kills eight logs of bacteria. Metallic silver kills less than one log of bacteria in 9 h. These findings support the novel concept whereby oxide formation, metal ion dissolution, and a Pearson soft character are the key factors for a metal to be antibacterial. Based on these parameters, copper and cadmium are expected to be the two most antibacterial metals.

Local Effects on Airway Inflammation and Systemic Uptake of 5 nm PEGylated and Citrated Gold Nanoparticles in Asthmatic Mice

Nanotechnology is showing promise in many medical applications such as drug delivery and hyperthermia. Nanoparticles administered to the respiratory tract cause local reactions and cross the blood-air barrier, thereby providing a means for easy systemic administration but also a potential source of toxicity. Little is known about how these effects are influenced by preexisting airway diseases such as asthma. Here, BALB/c mice are treated according to the ovalbumin (OVA) asthma protocol to promote allergic airway inflammation. Dispersions of polyethylene-glycol-coated (PEGylated) and citrate/tannic-acid-coated (citrated) 5 nm gold nanoparticles are applied intranasally to asthma and control groups, and (i) airway resistance and (ii) local tissue effects are measured as primary endpoints. Further, nanoparticle uptake into extrapulmonary organs is quantified by inductively coupled plasma mass spectrometry. The asthmatic precondition increases nanoparticle uptake. Moreover, systemic uptake is higher for PEGylated gold nanoparticles compared to citrated nanoparticles. Nanoparticles inhibit both inflammatory infiltrates and airway hyperreactivity, especially citrated gold nanoparticles. Although the antiinflammatory effects of gold nanoparticles might be of therapeutic benefit, systemic uptake and consequent adverse effects must be considered when designing and testing nanoparticle-based asthma therapies.

Recovery rate and homogeneity of doping europium into luminescent metal hydrides by chemical analysis

During the investigation of concentration dependent properties of phosphors, such as emission intensities, the knowledge of the activator ion concentration is of great importance. Herein we present a study on recovery rate and homogeneity of the activator ion concentration by chemical analysis in luminescent europium doped metal hydrides. The analysis method was established on the model system EuxSr1−xH2 and applied to brightly emitting hydridic perovskites LiMH3:Eu2+ and LiMD3:Eu2+ (M = Sr, Ba). The nominal activator ion concentrations calculated from initial weights are in good agreement with those determined via ICP-MS for 10−3% ≤ x both for the hydrides (deuterides) and the parent alloys. The synthesis protocol thus allows a reliable method for reproducibly doping europium into metal hydrides. Luminescence spectra of LiEuxSr1−xH3 with x = 0.0037% show a broad band emission at room temperature typical for Eu2+ 4f65d1–4f7 transitions. Below 80 K, a vibronic fine structure is observed with vibrational coupling frequencies of approximately 100, 370 and 970 cm−1.

Speciation via Hyphenation-Metal Speciation in Geological and Environmental Samples by CE-ICP-MS

This review deals with different aspects of analytical speciation methods developed for metals and metal-containing biomolecules or metal complexes with natural organic and inorganic matter in geological and environmental samples. An overview of recent studies dealing with metal speciation in various geological and environmental sample matrices is presented. The focus of analytical speciation methods is limited to capillary electrophoresis (CE) hyphenated with Inductively Coupled Plasma (ICP) detection techniques. The main aspects discussed in this review are the separation and detection step for the metal species. Possible influences of the applied separation technique on the metal speciation have been considered. Prominent exampes are, the metal-NOM (natural organic matter) complex stability during the separation step by the use of CE or the problem of ion-exchange and adsorption processes in the case of silica tubes as CE-capillaries. Additionally, different matrix effects in ICP-MS analysis will be discussed. Furthermore, the major drawback of speciation analysis is the lack of suitable reference or standard materials for the purpose of quality assurance. Therefore, quantification and verification of separation efficiency and accuracy for both the separation and detection step of the species have been evaluated, too.

Europium (III) and Uranium (VI) complexation by natural organic matter (NOM): Effect of source

For the safe long‐term storage of high‐level radioactive waste (HLW), detailed information about geo‐chemical behavior of radioactive and toxic metal ions under environmental conditions is important. Natural organic matter (NOM) can play a crucial role in the immobilization or mobilization of these metal ions due to its complexation and colloid formation tendency. In this study, the complexation of europium (as chemical homologue of trivalent actinides such as americium) and uranium (as main component of HLW) by ten humic acids (HA) from different sources and Suwannee NOM river extract has been analyzed. Capillary electrophoresis in combination with inductively coupled plasma mass spectrometry has been used for the evaluation of complex stability constants log β. In order to determine the complex stability constants a conservative single site model was used in this study. In dependence of their source and thus of NOM structure the log β values for the analyzed humic acids are in the range of 6.1–7.0 for Eu(III) and 5.2–6.4 for U(VI) (UO22+), respectively. In contrast to the results for HA the used Suwannee river NOM reveals log β values in the range of nearly two orders of magnitude lower (4.6 for Eu3+ and 4.5 for UO22+) under the geochemical conditions applied in this study.

Crystal structure of monoclinic samarium and cubic europium sesquioxides and bound coherent neutron scattering lengths of the isotopes 154Sm and 153Eu

Abstract The crystal structures of monoclinic samarium and cubic europium sesquioxide, Sm2O3 and Eu2O3, were reinvestigated by powder diffraction methods (laboratory X-ray, synchrotron, neutron). Rietveld analysis yields more precise structural parameters than previously known, especially for oxygen atoms. Interatomic distances d(Sm–O) in Sm2O3 range from 226.3(4) to 275.9(2) pm [average 241.6(3) pm] for the monoclinic B type Sm2O3 [space group C2/m, a = 1418.04(3) pm, b = 362.660(7) pm, c = 885.48(2) pm, β = 100.028(1)°], d(Eu–O) in Eu2O3 from 229.9(2) to 238.8(2) pm for the cubic bixbyite (C) type [space group Ia3̅, a = 1086.87(1) pm]. Neutron diffraction at 50 K and 2 K did not show any sign for magnetic ordering in Sm2O3. Isotopically enriched 154Sm2O3 and 153Eu2O3 were used for the neutron diffraction work because of the enormous absorption cross section of the natural isotopic mixtures for thermal neutrons. The isotopic purity was determined by inductively coupled plasma – mass spectrometry to be 98.9% for 154Sm and 99.8% for 153Eu. Advanced analysis of the neutron diffraction data suggest that the bound coherent scattering lengths of 154Sm and 153Eu need to be revised. We tentatively propose bc(154Sm) = 8.97(6) fm and bc(153Eu) = 8.85(3) fm for a neutron wavelength of 186.6 pm to be better values for these isotopes, showing up to 8% deviation from accepted literature values. It is shown that inaccurate scattering lengths may result in severe problems in crystal structure refinements causing erroneous structural details such as occupation parameters, which might be critically linked to physical properties like superconductivity in multinary oxides.

Antimicrobial properties of ternary eutectic aluminum alloys

Several Escherichia coli deletion mutants of the Keio collection were selected for analysis to better understand which genes may play a key role in copper or silver homeostasis. Each of the selected E. coli mutants had a deletion of a single gene predicted to encode proteins for homologous recombination or contained functions directly linked to copper or silver transport or transformation. The survival of these strains on pure copper surfaces, stainless steel, and alloys of aluminum, copper and/or silver was investigated. When exposed to pure copper surfaces, E. coli ΔcueO was the most sensitive, whereas E. coli ΔcopA was the most resistant amongst the different strains tested. However, we observed a different trend in sensitivities in E. coli strains upon exposure to alloys of the system Al–Ag–Cu. While minor antimicrobial effects were detected after exposure of E. coli ΔcopA and E. coli ΔrecA to Al–Ag alloys, no effect was detected after exposure to Al–Cu alloys. The release of copper ions and cell-associated copper ion concentrations were determined for E. coli ΔcopA and the wild-type E. coli after exposure to pure copper surfaces. Altogether, compared to binary alloys, ternary eutectic alloys (Al–Ag–Cu) had the highest antimicrobial effect and thus, warrant further investigation.

Simultaneous quantification of iodine and high valent metals via ICP-MS under acidic conditions in complex matrices

The determination of iodine as a main fission product (especially the isotopes I-129 and I-131) of stored HLW in a disposal beside its distribution as a natural ingredient of many different products like milk, food and seawater is a matter of particular interest. The simultaneous ICP-MS determination of iodine as iodide together with other elements (especially higher valent metal ions) relevant for HLW is analytically very problematic. A reliable ICP-MS quantification of iodide must be performed at neutral or alkaline conditions in contrast to the analysis of metal ions which are determined in acidic pH ranges. Herein, we present a method to solve this problem by changing the iodine speciation resulting in an ICP-MS determination of iodide as iodate. The oxidation from iodide to iodate with sodium hypochlorite at room temperature is a fast and convenient method with flexible reaction time, from one hour up to three days, thus eliminating the disadvantages of quantifying iodine species via ICP-MS. In the analysed concentration range of iodine (0.1-100µgL-1) we obtain likely quantitative recovery rates for iodine between 91% and 102% as well as relatively low RSD values (0.3-4.0%). As an additional result, it is possible to measure different other element species in parallel together with the generated iodate, even high valent metals (europium and uranium beside caesium) at recovery rates in the same order of magnitude (93-104%). In addition, the oxidation process operates above pH 7 thus offering a wide pH range for sample preparation. Even analytes in complex matrices, like 5M saline (NaCl) solution or artificial cement pore water (ACW) can be quantified with this robust sample preparation method.