Determination of refractive and volatile elements in sediment using laser ablation inductively coupled plasma mass spectrometry

Wet-milling protocol was employed to produce pressed powder tablets with excellent cohesion and homogeneity suitable for laser ablation (LA) analysis of volatile and refractive elements in sediment. The influence of sample preparation on analytical performance was also investigated, including sample homogeneity, accuracy and limit of detection. Milling in volatile solvent for 40 min ensured sample is well mixed and could reasonably recover both volatile (Hg) and refractive (Zr) elements. With the exception of Cr (−52%) and Nb (+26%) major, minor and trace elements in STSD-1 and MESS-3 could be analysed within ±20% of the certified values. Comparison of the method with total digestion method using HF was tested by analysing 10 different sediment samples. The laser method recovers significantly higher amounts of analytes such as Ag, Cd, Sn and Sn than the total digestion method making it a more robust method for elements across the periodic table. LA-ICP-MS also eliminates the interferences from chemical reagents as well as the health and safety risks associated with digestion processes. Therefore, it can be considered as an enhanced method for the analysis of heterogeneous matrices such as river sediments.     

Recent developments in electrochemical water oxidation

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Design of a tool for injecting organic waste slurries in soil

The object of the study was to design a tool for the purpose of cutting, loosening and redepositing a sufficient soil volume to be mixed with a specified quantity of organic waste slurry such that the slurry would be completely covered. Laboratory tests were conducted to determine the best tool shape for this function and to minimize the draft force required in operation. The results of full scale field tests are also shown, including the comparison of draft force measurements with values predicted from mechanics theory.     

The mechanics of soil cutting by a rotating wire

The cutting of soil by a rotating wire analogous to the tip of a rotary tiller blade while cutting a two-dimensional soil slice over a range of ‘fetch-ratios’ (bite length/depth-ratios) in a quasi-static condition is presented. A theoretical models based on Mohr-Coloumb soil mechanics has been proposed to predict forces on the wire (tip). The model is dependent upon observed passive general shear failure of the soil slice towards the curved free surface of a previous cut and the lateral local shear failure towards the undeformed soil. The predicted forces in a frictional soil and in a pure cohesive medium (artificial clay) agreed well with experimental results.     

A Cleavable Crosslinking Strategy for Commodity Polymer Functionalization and Generation of Reprocessable Thermosets

Covalently crosslinked polymeric materials, known as thermosets, possess enhanced mechanical strength and thermal stability relative to the corresponding uncrosslinked thermoplastics. However, the presence of covalent inter-chain crosslinks that makes thermosets so attractive is precisely what makes them so difficult to reprocess and recycle. Here, we demonstrate the introduction of chemically cleavable groups into a bis-diazirine crosslinker. Application of this cleavable crosslinker reagent to commercial low-functionality polyolefins (or to a small-molecule model) results in the rapid, efficient introduction of molecular crosslinks that can be uncoupled by specific chemical inputs. These proof-of-concept findings provide one potential strategy for circularization of the thermoplastic/thermoset plastics economy, and may allow crosslinked polyolefins to be manufactured, used, reprocessed, and re-used without losing value. As an added benefit, the method allows the ready introduction of functionality into non-functionalized commodity polymers.     

A Raman spectroscopic study of the uranyl phosphate mineral bergenite

Raman spectroscopy at 298 and 77 K of bergenite has been used to characterise this uranyl phosphate mineral. Bands at 995, 971 and 961 cm-1 (298 K) and 1006, 996, 971, 960 and 948 cm-1 (77K) are assigned to the nu1(PO4)3- symmetric stretching vibration. Three bands at 1059, 1107 and 1152 cm-1 (298 K) and 1061, 1114 and 1164 cm-1 (77 K) are attributed to the nu3(PO4)3- antisymmetric stretching vibrations. Two bands at 810 and 798 cm-1 (298 K) and 812 and 800 cm-1 (77 K) are attributed to the nu1 symmetric stretching vibration of the (UO2)2+ units. Bands at 860 cm-1 (298 K) and 866 cm-1 (77 K) are assigned to the nu3 antisymmetric stretching vibrations of the (UO2)2+ units. UO bond lengths in uranyls, calculated using the wavenumbers of the nu1 and nu3(UO2)2+ vibrations with empirical relations by Bartlett and Cooney, are in agreement with the X-ray single crystal structure data. Bands at (444, 432, 408 cm-1) (298 K), and (446, 434, 410 and 393 cm-1) (77 K) are assigned to the split doubly degenerate nu2(PO4)3- in-plane bending vibrations. The band at 547 cm-1 (298 K) and 549 cm-1 (77 K) are attributed to the nu4(PO4)3- out-of-plane bending vibrations. Raman bands at 3607, 3459, 3295 and 2944 cm-1 are attributed to water stretching vibrations and enable the calculation of hydrogen bond distances of >3.2, 2.847, 2.740 and 2.637 A. These bands prove the presence of structurally nonequivalent hydrogen bonded water molecules in the structure of bergenite.     

Analysis of organic aerosols collected on filters by Aerosol Mass Spectrometry for source identification

Aerosol Mass Spectrometers (AMS) are powerful tools in the analysis of the chemical composition of airborne particles, particularly organic aerosols which are gaining increasing attention. However, the advantages of AMS in providing on-line data can be outweighed by the difficulties involved in its use in field measurements at multiple sites. In contrast to the on-line measurement by AMS, a method which involves sample collection on filters followed by subsequent analysis by AMS could significantly broaden the scope of AMS application. We report the application of such an approach to field studies at multiple sites. An AMS was deployed at 5 urban schools to determine the sources of the organic aerosols at the schools directly. PM₁ aerosols were also collected on filters at these and 20 other urban schools. The filters were extracted with water and the extract run through a nebulizer to generate the aerosols, which were analyzed by an AMS. The mass spectra from the samples collected on filters at the 5 schools were found to have excellent correlations with those obtained directly by AMS, with r² ranging from 0.89 to 0.98. Filter recoveries varied between the schools from 40 to 115%, possibly indicating that this method provides qualitative rather than quantitative information. The stability of the organic aerosols on Teflon filters was demonstrated by analysing samples stored for up to two years. Application of the procedure to the remaining 20 schools showed that secondary organic aerosols were the main source of aerosols at the majority of the schools. Overall, this procedure provides accurate representation of the mass spectra of ambient organic aerosols and could facilitate rapid data acquisition at multiple sites where AMS could not be deployed for logistical reasons.     

Biomonitoring of 137Cs fall-out in Kudankulam coastal waters, Gulf of Mannar, India

Concentration of fall-out ¹³⁷Cs activity was monitored for a period of 3 years in coastline surface, near-shore surface and bottom waters of Kudankulam coast where a mega nuclear power station is being set up. Activity of ¹³⁷Cs was estimated by HPGe gamma spectrometry after chemical processing with AMP (ammonium molybdophosphate). The total ¹³⁷Cs concentration ranged from 1.2 to 1.6 mBq/L in coastline surface waters and between 0.75 and 1.4 mBq/L in near-shore surface and bottom waters. The data set followed a log-normal distribution. An insignificant relationship between ¹³⁷Cs and salinity, temperature and pH was noted. No yearly variation and no variation between surface and bottom waters were observed (p > 0.05) in the concentration of ¹³⁷Cs. The ¹³⁷Cs activity between seasons was found to be significantly different (p < 0.05).     

A study of three-nucleon transfer reactions on 18O

The reactions ¹⁸O¹¹B, ⁸Li)²¹Ne, ¹⁸O(¹²C, ⁹Be)²¹Ne and ¹⁸O(¹³C, ¹⁰B)²¹F have been studied, using beams of 115 MeV ¹¹B and ¹²C and 105 MeV ¹³C incident on a gas target. Shell-model calculations have been performed for ²¹Ne and ²¹F, for comparison with the experimental data. It is found that the data can be interpreted using the shell-model spectroscopic factors and a semiclassical reaction theory. Assignments are suggested for several previously unidentified high-spin states in ²¹Ne and ²¹F.     

Total synthesis of (S)-(-)-(E)-15,16-dihydrominquartynoic acid: a highly potent anticancer agent

The conjugated entriyne natural product, (S)-(E)-15,16-dihydrominquartynoic acid (1), is synthesized in five linear steps and 30% overall yield from the known aldehyde 11. The key step is a one-pot in situ desilylation/Cadiot-Chodkiewicz coupling reaction affording the entriyne unit. The bromoalkyne 6 with an omega-carboxylic acid group was found to undergo a copper-catalyzed cross-coupling reaction producing the desired diyne intermediate 10, while the corresponding omega-ester bromoalkyne 14 failed to couple with triethylsilylacetylene under a variety of conditions.