Volatile metal and metalloid species in gases from municipal waste deposits

We have detected volatile species of silicon, vanadium, arsenic, bromine, tin, antimony, tellurium, iodine, mercury, lead and bismuth in gases released from domestic waste deposits, using inductively coupled argon plasma mass spectrometry (ICP MS). By concurrent aspiration of a multielement standard solution for calibration, the element concentrations in deposit gas are found to be in the range from 0.1 ng m^?3 to 10 μg m^?3 gas. The global amount of some metal species emitted by this process may be of the order of several tons per year. These results suggest a biogeochemical pathway for the transfer of metals into the atmosphere via volatile species. This process may have significant influence on atmospheric cycling of metals as well as on metal toxicity within ecosystems.     

Can we trust mass spectrometry for determination of arsenic peptides in plants: comparison of LC–ICP–MS and LC–ES-MS/ICP–MS with XANES/EXAFS in analysis of <Emphasis Type="Italic">Thunbergia alata</Emphasis>

The weakest step in the analytical procedure for speciation analysis is extraction from a biological material into an aqueous solution which undergoes HPLC separation and then simultaneous online detection by elemental and molecular mass spectrometry (ICP-MS/ES-MS). This paper describes a study to determine the speciation of arsenic and, in particular, the arsenite phytochelatin complexes in the root from an ornamental garden plant Thunbergia alata exposed to 1 mg As L(-1) as arsenate. The approach of formic acid extraction followed by HPLC-ES-MS/ICP-MS identified different As(III)-PC complexes in the extract of this plant and made their quantification via sulfur (m/z 32) and arsenic (m/z 75) possible. Although sulfur sensitivity could be significantly increased when xenon was used as collision gas in ICP-qMS, or when HR-ICP-MS was used in medium resolution, the As:S ratio gave misleading results in the identification of As(III)-PC complexes due to the relatively low resolution of the chromatography system in relation to the variety of As-peptides in plants. Hence only the parallel use of ES-MS/ICP-MS was able to prove the occurrence of such arsenite phytochelatin complexes. Between 55 and 64% of the arsenic was bound to the sulfur of peptides mainly as As(III)(PC(2))(2), As(III)(PC(3)) and As(III)(PC(4)). XANES (X-ray absorption near-edge spectroscopy) measurement, using the freshly exposed plant root directly, confirmed that most of the arsenic is trivalent and binds to S of peptides (53% As-S) while 38% occurred as arsenite and only 9% unchanged as arsenate. EXAFS data confirmed that As-S and As-O bonds occur in the plants. This study confirms, for the first time, that As-peptides can be extracted by formic acid and chromatographically separated on a reversed-phase column without significant decomposition or de-novo synthesis during the extraction step.     

Microemulsions: Options To Expand the Synthesis of Inorganic Nanoparticles

Microemulsions (MEs) are ideal for obtaining high‐quality inorganic nanoparticles. As thermodynamically stable systems with a nanometer‐sized droplet phase that serves as a nanoreactor, MEs have obvious advantages for the synthesis of nanoparticles. MEs also have disadvantages, such as their complexity as multicomponent systems, the low amount of obtainable nanoparticles, their limited thermal stability, the fact that hydrolyzable or oxidizable compounds are often excluded from synthesis, the partly elaborate separation of nanoparticles, as well as the removal of surface‐adhered surfactants subsequent to synthesis. This Review presents some strategies to further expand the options of ME‐based synthesis of inorganic nanoparticles. This comprises the crystallization of nanoparticles in “high‐temperature MEs”, the synthesis of hollow nanospheres, the use of hydrogen peroxide or liquid ammonia as the polar droplet phase, and the synthesis of base metals and nitrides in MEs.     

Stereoelectronic effects in cyclic sulfoxides, sulfones, and sulfilimines: application of the Perlin effect to conformational analysis

The 1JC--H coupling constants in conformationally constrained sulfoxides, bissulfoxides, sulfoxide-sulfones, and sulfilimines derived from 2-benzylidene-1,3-dithiane and 2-(2,2-dimethylpropylidene)-1,3-dithiolane were measured by means of HMQC and HSQC NMR experiments and the Perlin effects were calculated. The type and the relative configuration of S==X groups (X= O, NTos) in these compounds have a strong influence on the magnitude of coupling constants for axial and equatorial C--H bonds, respectively. Axial S==O bonds give rise to a stereoelectronic effect on antiperiplanar axial C--H bonds. The resultant weakening of the respective C--H bonds leads to a smaller coupling constant than for a respective equatorial C--H bond. Equatorial S==O groups have an influence on beta-C--H bonds through a homoanomeric effect. Here, the axial C--H bond is weakened and a smaller coupling constant is measured. Sulfilimine groups show similar effects to sulfoxide groups.     

Pyridine-based Liquid-Phase Synthesis of Crystalline TiN and ZnSiN2 Nanoparticles

TiN and ZnSiN₂ nanoparticles are obtained via a novel pyridine-based synthesis route. This one-pot liquid-phase route strictly avoids all oxygen sources (including starting materials, surface functionalization, solvents), which is highly relevant in regard of the material purity and material properties. Colloidally stable suspensions of crystalline, small-sized TiN (5.4±0.4 nm) and ZnSiN₂ (5.2±1.1 nm) are instantaneously available from the liquid phase. Elemental analysis and electron energy loss spectroscopy confirm the purity of the compounds and specifically the absence of oxygen. The as-prepared ZnSiN₂ show yellowish emission (500-700 nm) already at room temperature with its maximum at 570 nm.     

The novel chain‐like anion ∞1[NaMo8O26(mim)2]3− in (Hmim)3[NaMo8O26(mim)2] (mim is 1‐methylimidazole)

Tris(1‐methylimidazolium) bis(1‐methylimidazole)hexacosaoxidooctamolybdatesodium, (C₄H₇N₂)₃[NaMo₈O₂₆(C₄H₆N₂)₂], prepared from an aqueous solution containing Na₂MoO₄ and 1‐methylimidazole, contains the novel chain‐like anion _∞¹[NaMo₈O₂₆(mim)₂]^{3 −} (mim is 1‐methylimidazole). The [Mo₈O₂₆(mim)₂]⁴⁻ building unit, which lies across a center of inversion, is comprised of eight edge‐sharing MoO₆ and MoO₅(N_mim) octahedra. These molybdate units are interlinked by sodium, itself exhibiting a sixfold coordination with O atoms.