Search results for "dilution"
showing 10 items of 242 documents
Substitution–dilution method to correct the matrix effect in multi-element quantitative analysis by X-ray fluorescence
2001
Abstract A mathematical model based on the dilution–addition method (DAM) for multi-elemental analysis using an X-ray fluorescence technique is proposed. The conditions for sample preparation do not require both the unknown and standard samples to be similar in composition and mineralogy, and the unknown sample is replaced quantitatively by the standard sample, hence the denomination substitution–dilution method (SDM). This method makes it possible to correct the matrix effect in multi-elemental quantitative analysis by X-ray fluorescence for each analyte. The proposed model presents hyperbolic behaviour of the experimental data when the X-ray fluorescence intensities are represented versus…
Determination of U-Pb ages of zircons by direct measurement of the 210Pb/206Pb ratio
1993
Abstract Precise measurements of the 210Pb/206Pb ratio in zircons permits, for the first time, the determination of complete U-Pb ages by measurement of Pb isotopes only, without determination of the U-Pb ratio by isotope dilution. The 238U daughter isotope 210Pb is generally in radioactive equilibrium with 238U; however, the very short half-life of 210Pb (22.3a) results in extremely low 210Pb/206Pb ratios of ∼ 10−8, especially for Archaean zircons. These ratios have been determined using a Finnigan MAT 262® mass spectrometer equipped with a high abundance sensitivity lens system (RPQ). The accuracy of the 210Pb method has been tested on nine different zircon samples with 207Pb/206Pb ages f…
Endotoxins in ophthalmic viscosurgical devices.
2003
Purpose To measure the endotoxin concentration (EC) of 25 commercially available, hyaluronic acid- and hydroxypropylmethylcellulose-based (HPMC) ophthalmic viscosurgical devices (OVDs). Methods The in vitro Limulus amebocyte lysate (LAL) assay, which indicates the presence of endotoxins originating from gram-negative bacteria, was used to determine the EC. The procedure was performed according to the European Pharmacopoeia/USP. EC including duplicate determinations, negative controls, dilution series with control standard endotoxin, dilution series with sample extract and positive sample control. Results 16 OVDs (Amvisc®, Amvisc® Plus, Biolon®, Coatel®, Healon®, Healon® GV, Healon®5, HPMC O…
Comparative LA-ICP-IDMS determinations of trace elements in powdered samples using laser ablation systems with low and high ablation rates
2004
The results of laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) with a special laser ablation system with high ablation rates (LINA-Spark-Atomiser), which was constructed for bulk analyses of solid samples, are compared with those obtained by one of the commonly used LA systems (UP213). Using different reference materials for validation it was demonstrated that the accuracy of LA-ICP-IDMS determinations of elements like Fe, Cu, Pb, and Zn by both systems is comparable in the concentration range of 10−2–10−6 g g−1, but the LINA-Spark-Atomiser also provides accurate results in the sub-μg g−1 range. IDMS enables accurate calibration of LA-ICP-MS determ…
Effect of the metal dilution on the thermal and light-induced spin transition in [FexMn1−x(bpp)2](NCSe)2: When T(LIESST) reaches T1/2
2008
International audience; The thermal and light-induced spin transition in [FexMn1−x(bpp)2](NCSe)2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) has been investigated by magnetic susceptibility, photomagnetism and diffuse reflectivity measurements. These complexes display a thermal spin transition and exhibit the light-induced excited spin state trapping (LIESST) effect at low temperature. For each mixed-crystal system, the thermal spin transition temperature, T1/2, and the relaxation temperature of the photo-induced high-spin state, T(LIESST), have been systematically determined. It appears that T1/2 decreases with the metal dilution while T(LIESST) remains unchanged, suggesting that the two interco…
Liposome Formation from Bile Salt–Lipid Micelles in the Digestion and Drug Delivery Model FaSSIFmod Estimated by Combined Time-Resolved Neutron and D…
2011
The flow of bile secretion into the human digestive system was simulated by the dilution of a bile salt-lipid micellar solution. The structural development upon the dilution of the fed state bile model FeSSIF(mod6.5) to the fasted state bile model FaSSIF(mod) was investigated by small-angle neutron scattering (SANS) and dynamic light scattering (DLS) in crossed beam experiments to observe small and large structures in a size range of 1 nm to 50 μm in parallel. Because of the physiologically low lipid and surfactant concentrations of 2.625 mM egg-phosphatidylcholine and 10.5 mM taurocholate the sensitivity of the neutron-structural investigations was improved by partial solvent deuteration w…
Nanoparticle structure development in the gastro‐intestinal model fluid FaSSIF mod6.5 from several phospholipids at various water content relevant fo…
2014
The characteristics of intestinal model fluids were investigated at conditions, which simulate the passage from the middle to the end of the duodenum. The formation and decay of liposomes and micelles in model bile fluids were studied, because of their role as an intermediate host for the resolution and uptake of hydrophobic drugs (BCS classes II, IV). The conditions, which may influence the formation of these nanoparticulate intermediates were studied, i.e., the lipid composition of the bile, the preparation method, the time of the passage through the modelled duodenum segment and the concentration, which results from the variable dilution of the bile by mixing with the transfer medium rep…
Etestw versus broth microdilution for ceftaroline MIC determination with Staphylococcus aureus: Results from PREMIUM, a European multicentre study
2017
Objectives: To compare the concordance of ceftaroline MIC values by reference broth microdilution (BMD) and Etest (bioMérieux, France) for MSSA and MRSA isolates obtained from PREMIUM (D372SL00001), a European multicentre study. Methods: Ceftaroline MICs were determined by reference BMD and by Etest for 1242 MSSA and MRSA isolates collected between February and May 2012 from adult patients with community-acquired pneumonia or complicated skin and soft tissue infections; tests were performed across six European laboratories. Selected isolates with ceftaroline resistance in broth (MIC >1 mg/L) were retested in three central laboratories to confirm their behaviour. Results: Overall concordance…
Normalization with Corresponding Naïve Tissue Minimizes Bias Caused by Commercial Reverse Transcription Kits on Quantitative Real-Time PCR Results
2016
Real-time reverse transcription polymerase chain reaction (PCR) is the gold standard for expression analysis. Designed to improve reproducibility and sensitivity, commercial kits are commonly used for the critical step of cDNA synthesis. The present study was designed to determine the impact of these kits. mRNA from mouse brains were pooled to create serial dilutions ranging from 0.0625 μg to 2 μg, which were transcribed into cDNA using four different commercial reverse-transcription kits. Next, we transcribed mRNA from brain tissue after acute brain injury and naïve mice into cDNA for qPCR. Depending on tested genes, some kits failed to show linear results in dilution series and revealed s…
A model of stepwise isovolaemic blood exchange in anaesthetised, spontaneously breathing rats to evaluate the oxygen transport efficiency of artifici…
2000
Our research pursues the production of hypo-oncotic artificial oxygen carriers, based on artificial covalently cross-linked hyperpolymeric mammalian haemoglobins. To evaluate their in vivo efficiency in oxygen delivery to the tissue we developed a small animal model of stepwise isovolaemic blood exchange in anaesthetised, spontaneously breathing rats. With the aid of a two-way respiratory micro valve for small animals the overall oxygen uptake by the tissue of the animal can be determined. Measurements of oxygen contents in arterial and mixed venous blood and of some further blood parameters together with known oxygen-binding characteristics of artificial and native oxygen carriers, permits…