The application of laser ablation for solid sample introduction to inductively coupled plasma-source mass spectrometry.

Inductively coupled plasma-source mass spectrometry (ICP-MS) is a powerful tool in multielemental analysis and has been used to find the composition of many diverse materials in recent years. Traditionally, samples are dissolved for introduction to the ICP by means of a pneumatic nebuliser. Laser ablation of solids for the direct introduction of sample material to the ICP is an attractive alternative to pneumatic nebulisation offering a number of analytical advantages, but particularly the speed and ease of working directly from the solid. In this work a ruby laser and the Surrey prototype ICP-mass spectrometer were used to assess the possibility of using a laser for solid sample introduction to ICP-MS. Systematic studies of the influence of parameters such as sample matrix composition, laser pulse energy, plasma gas flows, etc., on system response were undertaken with a view to optimising analytical performance. The feasibility of the analysis of metals, rocks, soils, sediments, leaf material, animal tissue, and some foodstuffs, has been investigated. This was achieved by the use of standard reference materials and intra and inter-analytical comparisons. For many matrices analyses can be obtained using integrations covering the full mass scan with calibration against matrix-matched standards. Such procedures allow the determination of analyte concentrations, in the mug g-1 range. Concentrations in the ng g-1 region can be detected using short mass scans. The main difficulty with the technique lies in the matrix dependent nature of the ablation process. Despite this, most of the anticipated advantages of the method are realised in practice. Laser ablation ICP-MS is likely to find increasing application for rapid trace analysis, particulary to high technology and biological materials

Optical Emission Study Of Reaction Mechanisms In The Deposition Of Nitrogen-containing Amorphous Hydrogenated Carbon Films

An expansion approach that is very simple for arbitrary profiles is presented. This requires only the diagolization of a matrix to obtain the eigen values. A couple-mode theory for calculation of diffraction of incident energy through inhomogeneous media, including gratings, and dispersion of electromagnetic energy propagating in photonic media is presented. A recursive R-matrix approach that is much more stable than a transfer T approach has been used. A transmission diffraction from a seven layer-deep square array of dielectric cylinders is calculated.1341901190

Effect of ion irradiation on the structural properties and hardness of A-C:H:SI:O:F films

Amorphous carbon-based thin films, a-C:H:Si:O:F, were obtained by plasma immersion ion implantation and deposition (PIIID) from mixtures of hexamethyldisiloxane, sulfur hexafluoride and argon. For PIIID the sample holder was biased with negative 25 kV pulses at 60 Hz. The main system parameter was the proportion of SF6 in the reactor feed, R-SF. To allow comparison to growth without intentional ion implantation, some films were also grown by plasma enhanced chemical vapor deposition (PECVD). The objectives were to investigate the effects of fluorine incorporation and ion implantation on the film's chemical structure, and principally on the surface contact angle, hardness and friction coefficient. Infrared and X-ray photo-electron spectroscopic analyses revealed that the films are essentially amorphous and polymer-like, and that fluorine is incorporated for any non-zero value of R-SF. Choice of R-SF influences film composition and structure but ion implantation also plays a role. Depending on R-SF, hydrophilic or hydrophobic films may be produced. Ion implantation is beneficial while fluorine incorporation is detrimental to hardness. For ion implanted films the friction coefficient falls about one third as R-SF is increased from 0 to 60%. Films prepared by PIIID without fluorine incorporation present fairly low friction coefficients and hardnesses greater than those of conventional polymers59115th Latin American Workshop on Plasma Physics (LAWPP) / 21st IAEA TM on Research Using Small Fusion Devices (RUSFD)2014-01COSTA RICAUniv Nacl Costa Rica, Instituto Tecnologico Costa Rica; Ad Astra Rocket Co; Int Atom Energy AgcySan Jos

Soil loss risk and habitat quality in streams of a meso-scale river basin

Soil loss expectation and possible relationships among soil erosion, riparian vegetation and water quality were studied in the São José dos Dourados River basin, State of São Paulo, Brazil. Through Geographic Information System (GIS) resources and technology, Soil Loss Expectation (SLE) data obtained using the Universal Soil Loss Equation (USLE) model were analyzed. For the whole catchment area and for the 30 m buffer strips of the streams of 22 randomly selected catchments, the predominant land use and habitat quality were studied. Owing mainly to the high soil erodibility, the river basin is highly susceptible to erosive processes. Habitat quality analyses revealed that the superficial water from the catchments is not chemically impacted but suffers physical damage. A high chemical purity is observed since there are no urban areas along the catchments. The water is physically poor because of high rates of sediment delivery and the almost nonexistence of riparian vegetation.Expectativa de perda de solo e possíveis relações entre erosão, vegetação ripária e qualidade da água foram estudados na bacia do rio São José dos Dourados (SP). Através de recursos de geoprocessamento e da Equação Universal de Perda de Solos, os dados sobre expectativa de perda de solo foram levantados. Para a área de drenagem total e a faixa tampão dos corpos d'água de 22 sub-bacias aleatoriamente selecionadas, analisou-se a cobertura do solo predominante e qualidade do habitat. Devido principalmente à alta erodibilidade do solo, a área estudada é altamente suscetível ao processo erosivo. As análises de qualidade da água revelaram que as águas superficiais das sub-bacias estão quimicamente não impactadas, mas fisicamente degradadas. A alta pureza química deve-se, possivelmente, à ausência de áreas urbanizadas ao longo das sub-bacias e as alterações nas características físicas são, possivelmente, decorrentes das altas taxas de transferência de sedimento aos corpos d'água e à quase ausência de mata ciliar

The application of laser ablation for solid sample introduction to inductively coupled plasma-source mass spectrometry.

Inductively coupled plasma-source mass spectrometry (ICP-MS) is a powerful tool in multielemental analysis and has been used to find the composition of many diverse materials in recent years. Traditionally, samples are dissolved for introduction to the ICP by means of a pneumatic nebuliser. Laser ablation of solids for the direct introduction of sample material to the ICP is an attractive alternative to pneumatic nebulisation offering a number of analytical advantages, but particularly the speed and ease of working directly from the solid. In this work a ruby laser and the Surrey prototype ICP-mass spectrometer were used to assess the possibility of using a laser for solid sample introduction to ICP-MS. Systematic studies of the influence of parameters such as sample matrix composition, laser pulse energy, plasma gas flows, etc., on system response were undertaken with a view to optimising analytical performance. The feasibility of the analysis of metals, rocks, soils, sediments, leaf material, animal tissue, and some foodstuffs, has been investigated. This was achieved by the use of standard reference materials and intra and inter-analytical comparisons. For many matrices analyses can be obtained using integrations covering the full mass scan with calibration against matrix-matched standards. Such procedures allow the determination of analyte concentrations, in the mug g-1 range. Concentrations in the ng g-1 region can be detected using short mass scans. The main difficulty with the technique lies in the matrix dependent nature of the ablation process. Despite this, most of the anticipated advantages of the method are realised in practice. Laser ablation ICP-MS is likely to find increasing application for rapid trace analysis, particulary to high technology and biological materials

Use of Saccharomyces cerevisiae immobilized in agarose gel as a binding agent for diffusive gradients in thin films

A new binding agent, consisting of the yeast Saccharomyces cerevisiae immobilized in agarose, is proposed for use in diffusive gradients in thin films (DGT). Different gel compositions, containing from 4.5% to 20% (m/v) of S. cerevisiae and 1.5-5.0% (m/v) of agarose, were prepared and tested for uptake of Cd(II). For gels containing 20% (m/v) of S. cerevisiae, a mass of 14,900 ng has been attributed as the uptake limit of Cd for each disk. Determination of the Cd retained in the binding agent was readily carried out using a slurry of the agarose-yeast disk introduced directly into the inductively coupled plasma optical emission spectrometer. The performance characteristics of the DGT samplers, which were assembled with the proposed binding agent (25 mm disk containing 20% of S. cerevisiae and 1.5% of agarose) and a diffusive layer of cellulose (chromatographic paper 3MM Chr of 25 mm diameter), were evaluated by measuring the Cd(II) uptake at various pH values and ionic strengths. Very consistent results were found within the pH range 4.5-7.5 and at ionic strengths >= 0.005 mol L(-1). The precision of DGT measurements was characterized by relative standard deviations of <8%. No changes in the uptake of Cd(II) were observed in the samplers that were assembled with recently prepared disks or 35-day-old stored disks. The proposed material has been applied to the analyses of river and sea water samples. For determination of Cd(II), excellent agreement between the results obtained from devices assembled with the proposed material and those assembled with conventional material (Chelex-100 resin) were obtained, strongly validating the use of the agarose-yeast gel disk as a new binding agent for DGT. (C) 2010 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Fluorinated polymer films from r.f. plasmas containing benzene and sulfur hexafluorine

Mixtures of C6H6 and SF6 were polymerized in an r.f. discharge. Actinometry (quantitative optical emission spectroscopy) was used to determine trends in the plasma concentrations of the species F, H and CH as a function of the proportion of SF6 in the feed. Infrared spectroscopy and electron spectroscopy for chemical analysis were employed to characterize the deposited material. Increasing proportions of SF6 in the feed produced increased fragmentation of the benzene molecules and greater fluorination of the deposited material. The deposition rate, as determined by optical interferometry, was found to be enhanced about 4 times by the presence of 10-20% SF6 in the feed. At 50% SF6 in the feed, deposition rates were greater than in pure C6H6 plasmas despite the (probably large) etching effect of atomic fluorine from the discharge. Relationships between the plasma composition, electron density and temperature, film composition and growth rate are discussed. © 1992