Search results for " PLASMA"

Iodine speciation in marine aerosols along a 30,000 km round-trip cruise path from Shanghai, China to Prydz Bay, Antarctica

2008

[1] Total suspended particle (TSP) samples were collected onboard a round-trip cruise from Shanghai, China to Prydz Bay, Antarctica from November 2005 to March 2006. Water soluble iodine species were measured using ion chromatography coupled to Inductively Coupled Plasma-Mass Spectrometry (IC-ICP-MS). The results reveal that soluble organic iodine (SOI) is the most abundant fraction, accounting for approximately 70 % of total soluble iodine (TSI) on average. One unidentified organic iodine (UOI) signal was present in almost all of the samples and was responsible for up to 38.3% of TSI. The abundance of inorganic iodine species, iodate and iodide, was less than 30% of TSI. Iodide was signifi…

Nematic elastomers: From a microscopic model to macroscopic elasticity theory

2008

A Landau theory is constructed for the gelation transition in cross-linked polymer systems possessing spontaneous nematic ordering, based on symmetry principles and the concept of an order parameter for the amorphous solid state. This theory is substantiated with help of a simple microscopic model of cross-linked dimers. Minimization of the Landau free energy in the presence of nematic order yields the neoclassical theory of the elasticity of nematic elastomers and, in the isotropic limit, the classical theory of isotropic elasticity. These phenomenological theories of elasticity are thereby derived from a microscopic model, and it is furthermore demonstrated that they are universal mean-fi…

Effect of physical aging on the low-frequency vibrational density of states of a glassy polymer

2003

The effects of the physical aging on the vibrational density of states (VDOS) of a polymeric glass is studied. The VDOS of a poly(methyl methacrylate) glass at low-energy (<15 meV), was determined from inelastic neutron scattering at low-temperature for two different physical thermodynamical states. One sample was annealed during a long time at temperature lower than Tg, and another was quenched from a temperature higher than Tg. It was found that the VDOS around the boson peak, relatively to the one at higher energy, decreases with the annealing at lower temperature than Tg, i.e., with the physical aging.

Enhancing the mechanical performance of polymer based nanocomposites by plasma-modification of nanoparticles

2012

Abstract The possibility of enhancing the mechanical performance of two different polymer-based nanocomposites using polyamide 6 (PA6) and poly[ethylene-co-(vinyl acetate)] (EVA) as matrices was investigated. The nanofillers used were, respectively, either carbon nanotubes (CNTs) or an organically modified montmorillonite (Cloisite 15A), both previously modified by plasma treatment to introduce polar moieties. The nanofillers were fully characterized by Raman spectroscopy, XPS, FT-IR and XRD, demonstrating their effective modification with oxygenated groups. The nanocomposites were prepared by melt processing in order to obtain films and fibres. The mechanical tests carried out on the nanoc…

Determination of zirconium traces in polymers by ICP-IDMS - a powerful and fast method for routine testing of zirconium residues in polyolefins

1999

Zirconium trace analyses play an important role for polyolefins produced by modern catalytic processes with zirconium metallocenes. A reliable and fast routine testing method by inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) was therefore developed, which allows the determination of zirconium in polymers down to the low ng/g level. With respect to its precision, accuracy, and time-consumption this method is suitable for routine testing of production processes. A spike solution, enriched in the stable isotope 91Zr, was prepared and used for the isotope dilution procedure, which has the advantage of being an internal “one point” calibration method. The polyolefin sam…

Trace element determination in sediments: a comparative study between neutron activation analysis (NAA) and inductively coupled plasma-mass spectrome…

2000

An inductively coupled plasma-mass spectrometry (ICP-MS) method has been employed for trace element determination in five real sediment samples and a standard reference material. These samples were mineralized by dry ashing at 550°C and fused at 1100°C for 30 min with lithium metaborate. Dissolved samples were measured by a semiquantitative methodology with external calibration and with Rh as an internal standard. More than 50 elements have been measured. As a reference technique, a direct analysis of the solid samples was carried out by neutron activation analysis. Results obtained by ICP-MS have been compared with those obtained by neutron activation analysis (NAA) by applying the paired …

Nano‐Powdered Calcium Carbonate Reference Materials: Significant Progress for Microanalysis?

2019

Validation of Methylmercury Determinations in Aquatic Systems by Alkyl Derivatization Methods for GC Analysis Using ICP-IDMS

2001

Isotope dilution mass spectrometry (IDMS), using an inductively coupled plasma quadrupole mass spectrometer (ICPMS) and a species-specific methylmercury spike was applied to validate the commonly used GC method for methylmercury (MeHg+) determination, which is based on the formation of volatile methylethylmercury by derivatization with NaBEt4. The spike compound, Me201Hg+, was synthesized by reaction of 201Hg-enriched mercury chloride with methylcobalamin. By analyzing different environmental aquatic samples, it was found that in most cases, transformation of MeHg+ into elemental mercury (Hg0) took place. From investigations of synthetic solutions, it could be followed that halide ions are …

Bestimmung von Tri-n-butylphosphat in Plasmapräparaten nach Festphasenextraktion und Kapillar-Gaschromatographie

1988

A simple method for the quantitative determination of tri-n-butylphosphate in blood plasma preparations is described. The sample is passed through an octadecyl extraction column from which tri-n-butylphosphate is eluted with chloroform. By capillary GC 50 micrograms/l tri-n-butylphosphate can be detected with a recovery of more than 90%.

Stability of 11-Nor-Δ9-carboxy-tetrahydrocannabinol Glucuronide in Plasma and Urine Assessed by Liquid Chromatography-Tandem Mass Spectrometry

2002

Abstract Background: Unconjugated 11-nor-Δ9-carboxy-tetrahydrocannabinol (THCCOOH) in blood and urine has been proposed as a valuable marker, but the glucuronide (THCCOOglu) is present in considerably higher concentrations than the parent drug. Acyl glucuronides have been shown to be potentially reactive conjugates, which may affect the in vitro metabolite pattern. Methods: Extraction procedures and a liquid chromatography-tandem mass spectrometry assay were developed and validated to investigate the stability of THCCOOglu in urine and plasma. Plasma and urine samples with added THCCOOglu were stored at −20, 4, 20, and 40 °C up to 10 days. Results: The glucuronide was stable at −20 °C in bo…