Search results for "LIMIT"
showing 10 items of 2826 documents
Multi-element trace determinations in pure alkaline earth fluoride powders by high-resolution ICP-MS using wet-chemical sample preparation and laser …
2003
Four alternative analytical procedures for the determination of ten important trace impurities (Mg, Cr, Fe, Cu, Zn, Sr, Zr, Cd, Ba, and Pb) in pure alkaline earth fluoride powders were applied using high-resolution inductively coupled plasma mass spectrometry (ICP-MS). Two procedures are based on a wet-chemical microwave digestion with boric acid and quantification by the standard addition technique and isotope dilution mass spectrometry (IDMS), respectively. In addition, analyses are also performed by laser ablation as a direct solid sampling technique applying matrix-matched external calibration as well as isotope dilution of the powdered sample. For most elements good agreement between t…
Development of an isotope dilution laser ablation ICP-MS method for multi-element determination in crude and fuel oil samples
2009
An inductively coupled plasma isotope dilution mass spectrometric (ICP-IDMS) method with direct introduction of the isotope-diluted sample into the plasma by laser ablation was developed for accurate, sensitive, fast, and simultaneous determination of trace metals in different oil samples. Metallo-organic solutions of isotope spikes (50V, 53Cr, 65Cu, 57Fe, 62Ni, 68Zn, 113Cd, 117Sn, and 206Pb) were prepared from corresponding aqueous stock solutions by using liquid–liquid extraction of complexed metal ions in isobutyl methyl ketone. The isotope-diluted sample was absorbed by a cellulose material, which was fixed in a special PTFE holder for ablation, using a laser system with high ablation r…
A study on the adsorption voltammetry of titanium with various heterocyclic azo-compounds
1994
The voltammetric behaviour of various heterocyclic azo-compounds and their Ti-complexes was investigated at a stationary Hg electrode. In moderately acidic solutions Ti(IV) reacts with pyridylazo-compounds (PAR, 5-Br-PADAP, PAN), thiazolylazo-compounds (TAR, 5-Me-TAR, TAN, 4-Me-TAP) and pyrazolylazo-compounds (MDR, ERB) to form Ti-complexes, which are strongly adsorbed onto the Hg-electrode. These complexes are reduced at potentials more negative than those corresponding to the reduction of their respective ligands. The conditions for determining titanium by adsorption voltammetry using TAR and MDR as complexing agents were investigated in detail, as was the influence of foreign ions on the…
Determination of titanium by adsorption-voltammetry with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP)
1990
The 1:1 complex between titanium (IV) and 5-Br-PADAP can be used to determine titanium by adsorption voltammetry at a stationary Hg-electrode. The experimental conditions for the determination are described. The detection limit is 3×10−10 mol/l Ti (0.015 ppb). Calibration curves are linear for solutions containing 4×10−10 to 5×10−8 mol/l Ti(IV) and an enrichment time of 3 min. The influence of foreign ions was investigated. The determination can be carried out in the presence of a 5000-fold excess of iron.
Flow injection flame atomic spectrometric determination of iron, calcium, magnesium, sodium and potassium in ceramic materials by using a variable-vo…
1993
A series of different ceramic materials, such as porcelain, feldspar, kaolin, varnish, clay and stoneware have been analyzed. Iron, calcium and magnesium have been determined in these materials by flame atomic absorption and sodium and potassium by flame emission. The use of a variable-volume injector enables one to carry out these analyses in a flow system (after fusion of samples with lithium metaborate) and does not require different dilutions for the determination of each type of sample considered, nor the use of different flow injection manifolds. The developed procedure provides a limit of detection of 100 μg/l for Na, 70 μg/l for Ca, 50 μg/l for both Fe and K and 8 μg/l for Mg. The c…
Atomic-absorption spectrometric determination of calcium, magnesium and potassium in leaf samples after decomposition with molten sodium hydroxide
1991
Abstract The decomposition of standard leaf samples of varied origin and nature by fusion with sodium hydroxide in an open system has been studied. The use of sodium nitrate as an auxiliary agent facilitated the mineralization of most of the samples. The solutions obtained were analysed for calcium, magnesium and potassium by flame atomic-absorption spectrometry. The method is fast and quite precise, with absolute standard deviations of 0.04–0.13, 0.002-0.03 and 0.04–0.12% for calcium, magnesium and potassium contents of O.8-5.0, 0.13–0.48 and 0.36–2.2% respectively. The limits of detection (μg/ml) in the determination step were 0.10 for calcium, 0.011 for magnesium, and 0.09 for potassium.
Introducing a new and rapid microextraction approach based on magnetic ionic liquids: Stir bar dispersive liquid microextraction
2017
With the aim of contributing to the development and improvement of microextraction techniques, a novel approach combining the principles and advantages of stir bar sorptive extraction (SBSE) and dispersive liquid-liquid microextraction (DLLME) is presented. This new approach, termed stir bar dispersive liquid microextraction (SBDLME), involves the addition of a magnetic ionic liquid (MIL) and a neodymium-core magnetic stir bar into the sample allowing the MIL coat the stir bar due to physical forces (i.e., magnetism). As long as the stirring rate is maintained at low speed, the MIL resists rotational (centrifugal) forces and remains on the stir bar surface in a manner closely resembling SBS…
Trace determination of volatile polycyclic aromatic hydrocarbons in natural waters by magnetic ionic liquid-based stir bar dispersive liquid microext…
2017
In this work, a novel hybrid approach called stir bar dispersive liquid microextraction (SBDLME) that combines the advantages of stir bar sorptive extraction (SBSE) and dispersive liquid-liquid microextraction (DLLME) has been employed for the accurate and sensitive determination of ten polycyclic aromatic hydrocarbons (PAHs) in natural water samples. The extraction is carried out using a neodymium stir bar magnetically coated with a magnetic ionic liquid (MIL) as extraction device, in such a way that the MIL is dispersed into the solution at high stirring rates. Once the stirring is ceased, the MIL is magnetically retrieved onto the stir bar, and subsequently subjected to thermal desorptio…
Quantitation of talinolol in rat plasma by LC-MS-MS.
2010
The aim of this study was to develop and validate an assay based on liquid chromatography-tandem mass spectrometry to quantitate talinolol in rat plasma. After a simple protein precipitation step, separation was performed by reversed-phase liquid chromatography using gradient elution with acetonitrile-water-formic acid. Electrospray ionization in the positive ion mode with multiple reaction monitoring was used to analyze talinolol employing propranolol as internal standard. The calibration curve for talinolol was linear over the concentration range 1-250 ng/mL with a correlation coefficient0.995. The method was sensitive (limit of quantitation, 1 ng/mL) and had acceptable accuracy (85-115% …
Optimization of clean-up procedure for patulin determination in apple juice and apple purees by liquid chromatography
2009
Patulin (PAT) is a mycotoxin produced in fruits, mainly in apples, by several fungal species that can be carried into industrial apple juice by-products during factory processing. An analytical method for determination of PAT in apple juice and another one for determination of this compound in apple purees and apple compotes by liquid chromatography are proposed in the present paper. These methods have better precision and sensitivity than previously reported methods and focus mainly on extraction and clean-up. To accomplish analytical methods with higher accuracy, lower limits of detection and simpler procedures for application in quality control of the goods, different extraction and clea…