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For isotope ratio applications where an internal isotope ratio precision >0.05–0.1% relative standard deviation suffices, single-collector inductively coupled plasma mass spectrometry (ICPMS) is fit-for-purpose, but for detecting more subtle variations in the natural isotopic composition of a target element, only multi-collector ICPMS (MC-ICPMS) can compete with thermal ionization mass spectrometry (TIMS). While as a result of the extensive sample preparation (analyte isolation) preceding TIMS and the "softer" ionization in vacuum, spectral interferences only seldom occur with this technique, their occurrence is recognized to be the most important drawback of ICPMS. This paper discusses high mass resolution and chemical resolution in a collision or dynamic reaction cell as powerful and versatile means to overcome spectral overlap and illustrates how their introduction has led to a substantial extension of the application range of ICPMS for isotope ratio applications. High mass resolution is the most elegant and straightforward way to overcome the problem of spectral overlap. Offering the possibility to operate the mass analyzer at a higher mass resolution, while at the same time preserving the flat-topped or trapezoidal peak shape required for highly precise isotope ratio measurements, was a challenge for the manufacturers of MC-ICPMS instrumentation. It will be discussed how these apparently contradicting requirements could be fulfilled simultaneously and an overview of the current situation will be given. Chemical resolution in a collision or dynamic reaction cell is an alternative to high mass resolution for overcoming spectral overlap. Real-life examples will be given to illustrate how also this approach can be used to advantage in isotope ratio work. Despite the greater flexibility and straightforwardness of high mass resolution, some situations will be discussed where chemical resolution is to be preferred. Finally, some desires as to future instrumentation are formulated. [ABSTRACT FROM AUTHOR]

Experiments modelling photolytic decomposition of methylmercury chloride in aqueous solutions of different chemical composition have been performed. Ion-exchange chromatographic separation using Chelex®100 resin was used in order to separate methylmercury from inorganic mercury prior to the isotope ratio measurements by solution nebulization multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). The performance of the chromatographic separation has been evaluated in terms of recovery of both methylmercury and inorganic Hg using synthetic solutions. Both mass-dependent and mass-independent fractionation of Hg isotopes concomitant with the decomposition process have been observed. Mass-independent Hg isotope fractionation (MIF) resulted in selective enrichment of 199Hg and 201Hg relative to the other isotopes in the methylmercury molecules and has been attributed to the magnetic isotope effect. The highest extent of MIF of Hg isotopes, expressed as Δ199Hg and Δ201Hg values, has been observed in acidified solution with low concentration of total dissolved solids (TDS). Progressive decrease in Δ199Hg and Δ201Hg values in acidified solution with higher concentration of TDS, alkaline solutions of both low and high concentration of TDS, and in a solution of ascorbic acid has been attributed to suppression of the radical pair reaction mechanism, responsible for the occurrence of the magnetic isotope effect, by substances acting as radical scavengers, such as OH−or ascorbic acid. The data obtained in this study demonstrate the significance of spin chemistry effects in the isotope fractionation of mercury. [ABSTRACT FROM AUTHOR]

Advances in heterogeneous catalysis are driven by the structure-function relationships that define catalyst performance (i.e., activity, selectivity, lifetime). To understand these relationships, cooperative research is required: prediction and analysis using computational models, development of new synthetic methods to prepare specific solid-state compositions and structures, and identification of catalytically active site(s), surface-bound intermediates, and mechanistic pathways. In the application of deoxygenating and upgrading biomass pyrolysis vapors, a fundamental understanding of the factors that favor C-O bond cleavage and C-C bond formation is still needed. In this review, we focus on recent advances in heterogeneous catalysts for hydrodeoxygenation of biomass pyrolysis products. Focus is placed on studies that made use of model compounds for comparisons of catalysts and the reaction networks they promote. Applications of transition metal sulfide catalysts for deoxygenation processes are highlighted, and compared to the performances of noble metal and metal carbide, nitride, and phosphide catalysts. In general, it is found that bifunctional catalysts are required for deoxygenation in a single reactor, with bifunctionality achieved on the catalyst or in conjunction with the catalyst support. Catalysts that activate hydrogen well will be preferred for ex situ catalytic pyrolysis conditions (upgrading downstream of pyrolysis reactor prior to condensation of bio-oil, pressures near atmospheric, temperatures between 350-500 °C). Supports that limit chemisorption of large reactants (leading to blockage of catalyst sites) should be employed. Finally, the stability of the catalyst and support in high-steam and low hydrogen-to-carbon environments will be critical. [ABSTRACT FROM AUTHOR]

In this paper a procedure is established to identify spectral bands that show similar behavior in two-dimensional correlation spectra. Slice spectra of bands that are affected in a single spectral event are highly similar. It is shown that this can be used to simplify the interpretation of two-dimensional (2D) correlation diagrams. One functional group frequently gives rise to multiple spectral bands in a Raman spectrum. In such occasions, the sequential order rules assign a sequential order, which is invalid, to the changes in these bands. We therefore apply cluster analysis to the slice spectra of bands with intensity changes during the experiment. Results indicate that cluster analysis of selected slice spectra can help in the interpretation of 2D correlation spectra in an intuitive and graphical way. The procedure should be used together with the widely used sequential order rules to determine the order of spectral events. The procedure enabled us to reveal the reaction steps in two simulated datasets and a dataset that comprises Raman spectra of oxidating latex of Lactarius fluens (Basidiomycota, Fungi). [ABSTRACT FROM AUTHOR]

Background. The Epidemiological Study Air Disaster in Amsterdam (ESADA) aimed to assess long-term health effects in professional assistance workers involved in the 1992 air disaster in Amsterdam. As part of ESADA indications of nephrotoxicity due to exposure to uranium from the balance weights of the crashed aircraft were assessed. Methods. Data of a historically defined cohort of 2499 (exposed and non-exposed) firefighters, police officers and hangar workers were collected 8.5 years after the disaster. Urinary uranium concentrations were determined by sector field inductively coupled plasma mass spectrometry. Urine albumin–creatinine ratio and fractional excretion of β2-microglobulin were calculated from a single-spot urine specimen and simultaneous blood sample. Exposed assistance workers were compared with their non-exposed colleagues, and associations between uranium and kidney function parameters were explored. Results. Median uranium concentrations were around 2 ng/g creatinine. Median values of albumin–creatinine ratio and fractional excretion of β2-microglobulin were well below the level for microalbuminuria and for tubular damage, respectively. No statistically significant differences between exposed and non-exposed workers were found in uranium concentrations and kidney function parameters, although exposed hangar workers had lower uranium concentrations. No statistically significant associations were found between uranium concentrations and kidney function parameters in the total cohort. Conclusions. Occupational exposure to the air disaster in Amsterdam was neither significantly associated with higher uranium concentrations, nor with disturbed kidney function parameters. In this large cohort of professional assistance workers, urinary uranium concentrations were in the low range compared with previously published reference populations. No indications of nephrotoxicity were found at urinary uranium concentrations around 2 ng/g creatinine. [ABSTRACT FROM AUTHOR]

We describe the possibility of using a microresonance Raman spectrometer combined with a microfluidic system and optical tweezers to study Escherichia coli (E. coli) overexpressing wild type (wt) neuroglobin (NGB) and its E7Leu mutant, respectively. NGB is a recently discovered heme protein and its function still is a matter of debate. So far, the protein has been studied in its purified form, and in vivo measurements on the single cell level could give more information. To study the feasibility of the combined techniques, the possibilities of the setup are investigated by taking spectra from single cells and clusters of cells. We find that the microresonance Raman technique enables studies of the wt NGB protein in a living cell under fluctuating aerobic and anaerobic conditions. E. coli cells overexpressing wt NGB are stable, and the reversible oxygenation-deoxygenation can be studied over a long period of time. Further, the experiment indicates the presence of an enzymatic system in the bacteria reducing the ferric form NGB. The study of E. coli cells overexpressing E7Leu NGB, on the other hand, gives insight into limiting factors of the setup, such as cell lysis, photoinduced chemistry, and protein concentrations. [ABSTRACT FROM AUTHOR]