Search results for "dilution"
showing 10 items of 242 documents
Use of thermal ionization isotope dilution mass spectrometry (TI-IDMS) as an oligo-element method for the determination of photographically relevant …
1998
Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used as an oligo-element method for the determination of Cr, Cd and Pb in photographic AgCl emulsions. After addition of an appropriate amount of isotopically enriched spikes (53Cr, 116Cd and 206Pb) to the solid samples, the latter were completely dissolved in NH3 solution, permitting isotopic exchange to take place. Thereafter, AgCl was selectively removed by precipitation, whereby ultrasonic treatment was used to enhance the recovery of the elements of interest. Despite the use of concentrated HNO3 and H2O2 during further sample processing, preliminary experiments indicated the presence of a substantial remainder of the o…
Application of stable isotopes and AF4/ICP-SFMS for simultaneous tracing and quantification of iron oxide nanoparticles in a sediment–slurry matrix
2016
One major challenge in nanomaterial analysis, especially in complex environmental matrices, is the unambiguous differentiation between natural and engineered nanomaterials (ENMs). Particularly with regard to the investigation of ENM's/engineered nanoparticle's (ENPs) fate, analytical methods are needed allowing for tracing and sensitive quantification. Several ENPs are metal-based and contain elements being omnipresent in environmental matrices (e.g., Al, Ti, Zn, Fe and non-metal Si) – hence, high background levels of these elements are expected, compromising sensitive detection. In this work we developed successfully a combined approach of stable isotope labeling (tracing) and reverse post…
Micropumping multicommutation turbidimetric analysis of waters
2007
Abstract A micropumping multicommutation manifold to perform turbidity determinations in waters is described. The procedure is based on the use of a combination of hydrazine sulfate and hexamethylenetetramine, to obtain an external standard of nephelometric turbidity units (NTU), which could compare the absorbance measurements at high wavelengths for samples with a calibration line obtained from a concentrated formazine standard diluted on-line. To minimize sample and reagent consumption and waste generation, the flow system was designed with two solenoid micro-pumps, one of them for the alternative introduction of the formazine standard and samples and the other one for the water carrier. …
Identification of ground water contaminations by landfills using precise boron isotope ratio measurements with negative thermal ionization mass spect…
1997
Precise boron isotope ratio measurements with negative thermal ionization mass spectrometry were used for the identification of ground water contaminations by leakages of landfills. BO 2 - thermal ions were produced to determine the 11 B/ 10 B isotope ratio, which was expressed as δ 11 B value in ‰ normalized to the standard reference material NIST SRM 951. For example, household waste influences the boron isotope ratio by specific components such as washing powder. In the case of one investigated landfill low δ 11 B values correlate well with high boron concentrations in contaminated seepage water samples and vice versa for uncontaminated ground water samples. Possible boron contributions …
Resolution of overlapped non-absorbing and absorbing solutes using either an absorption null-balance detection window or multivariate deconvolution a…
2004
Abstract Non-absorbing alkyl ether sulfates (AES) can be separated using anthraquinone-2-carboxylic acid (AQCA) as a probe; however, absorbing alkyl benzene sulfonates (ABS), if present, interfere indirect detection of most AES oligomers. Overcoming of this interference, as well as the simultaneous characterisation and evaluation of AES, fatty acids and ABS, was accomplished by using a diode-array detector and the procedures here discussed. First, it was shown that ABS can be made undetectable by using a 9 nm wide and 227 nm centred charge-absorptivity null-balance detection window (NBDW), where its contribution to the absorbance cancels the dilution effects that its presence induces on the…
Species-Specific GC/ICP-IDMS for Trimethyllead Determinations in Biological and Environmental Samples
2005
An accurate and sensitive species-specific isotope dilution GC/ICPMS method was developed for the determination of trimethyllead (Me3Pb+) in biological and environmental samples. A trimethyllead spike was synthesized from 206Pb-enriched metallic lead by reaction of lead halide with methyllithium and subsequent formation of trimethyllead iodide. The isotopic composition of the spike solution was determined by GC/ICPMS after derivatization with tetraethylborate, and its concentration was determined by reverse isotope dilution analysis. The species-specific GC/ICP-IDMS method was validated by reference material CRM 605 (urban dust) certified for Me3Pb+. The method was also applied to determine…
Direct FIA—AS determination of potassium and magnesium in cement samples by use of the slurries approach
1992
A direct procedure has been developed for the flame atomic determination of potassium and magnesium in cement samples. A 50-mg sample is dispersed in 25 ml of 0.13M nitric acid; 100 mul of this slurry is injected in a double channel FIA manifold simultaneously with 100 mul of a 10% (w/v) lanthanum solution. This procedure allows the rapid extraction of potassium and magnesium by leaching of the sample; nitric acid is not necessary if only potassium must be determined and the sample can be diluted with only distilled water. Aqueous standards are used. The manifold employed includes a well-stirred mixing chamber, which provides an adequate on-line dilution of the sample, in order to obtain em…
Risk factors for Lyme disease : A scale-dependent effect of host species diversity and a consistent negative effect of host phylogenetic diversity
2021
Biodiversity can influence disease risk. One example of a diversity-disease relationship is the dilution effect, which suggests higher host species diversity (often indexed by species richness) reduces disease risk. While numerous studies support the dilution effect, its generality remains controversial. Most studies of diversity-disease relationships have overlooked the potential importance of phylogenetic diversity. Furthermore, most studies have tested diversity-disease relationships at one spatial scale, even though such relationships are likely scale dependent. Using Lyme disease as a model system, we investigated the effects of host species richness and phylogenetic relatedness on the…
ETP/GDOP Behavior Study for N-Sensors Arrays ina Multilateration Radar System
2009
In this paper, we evaluated the ETP (Expected Theoretical Precision) and GDOP (Geometric Dilution Of Precision) enhancement related to the number of sensors in a Multilateration radar system. An introduction about the principles of the Multilateration radar system basis operation is described, then, the formulation for evaluation the ETP/GDOP of the 3D positioning is shown. We observed that the ETP and GDOP enhance with the increase of the number of sensors. A substantial improvement was obtained until nine sensors but, for more sensors that improvement is reduced. Results for a 75km×75km area are shown, including LAM (Local Area Multilateration) and WAM (Wide Area Multilateration) settings…
Nursing: more used medicines in the emergency rooms of hospitals
2007
El Servicio de Urgencias del C.H.G.U.V. cuenta con una plantilla de 84 Enfermeros/as. Una parte considerable de ellos es personal de nueva incorporación, de ahí que sea prioritaria la elaboración de protocolos de actuación. La administración de medicación intravenosa es sin duda una de las técnicas de mayor aplicación en los pacientes que acuden a Urgencias, que en nuestro Hospital oscila entre 550-600 atenciones diarias. Por ello nos planteamos, mediante la realización de reuniones de grupo, la elaboración del presente trabajo con el objetivo de elaborar un manual informativo sobre la medicación más habitual utilizada en nuestro Servicio de Urgencias; indicaciones, contraindicaciones, dilu…