Search results for "absorption."
showing 10 items of 2682 documents
Flow injection flame atomic absorption analysis of Fe and Mn in cement samples
1993
A new procedure has been developed for the determination of Fe and Mn in cements. It consists in dispersing 50 mg of the solid sample in 25 ml of 0.15 mol/l HNO3 and 0.12 mol/l HCl solution. Acid slurries are heated at 50°C for 10 min and then different volumes of the slurry are injected into a water carrier stream. This previous acid treatment leaches the elements to be determined and permits the use of acid solutions as standards. For the Mn determination, the use of a single line flow injection manifold provides a limit of detection of 0.03 mgl−1 and a dynamic range up to 6 mgl−1. For the determination of Fe, the on-line dispersion of samples, using a well stirred mixing chamber, increas…
Determination of chromium(III) and chromium(VI) in mineral water by bidirectional electrostacking and electrothermal atomic absorption spectrometry
2001
Abstract A feasibility investigation was carried out on the use of bidirectional electrostacking for simultaneous separation and pre-concentration of Cr(III) and Cr(VI) and their electrothermal atomic absorption spectrometry (ETAAS) determination. The bidirectional electrostacking manifold was improved, and the effects of sample tube cross-section and electrostacking time on the pre-concentration factor were investigated. Results indicate that the sample tube cross-section and electrostacking time are the main influence factors on the electrostacking pre-concentration, as well as the electric field strength and ionic mobility. The method developed was suitable for the simultaneous separatio…
Atomic absorption spectrometric determination of molybdenum in lubricating oils with use of emulsions
1985
Abstract Samples (0.1 g) containing molybdenum disulphide are digested with aqua regia or with a (1 + 1) hydrofluoric/nitric acid mixture, without complete destruction of the matrix, and the molybdenum is determined in an air/acetylene flame, after emulsification with a non-ionic surfactant (Nemol K-39). The detection limit is ca. 30 μg Mo g−1, and the r.s.d. is 2.9% for 6 analyses of a sample containing 6.5 mg Mo g−1.
On-line microwave oven digestion flame atomic absorption analysis of solid samples
1990
Abstract A manifold has been developed for on-line microwave oven digestion and flame atomic absorption spectrometric (FAAS) determination of metallic elements in solid samples. The use of a closed flow system permits sample treatment before analysis by FAAS, the direct injection of slurries avoids a filtration step and the interconnection of two conventional rotary injection valves allows the rapid introduction of samples and standards. The determination of lead in sewage sludge was employed as a test system for the proposed on-line sample digestion manifold. The procedure has a limit of detection of 0.2 μg Pb g−1.
A comparative study of flame atomic-absorption methods for determination of zinc in serum and blood plasma
1983
Seven selected methods for determination of zinc in blood plasma by flame atomic-absorption spectroscopy have been compared. Analytical characteristics such as sensitivity, detection limit, precision, analytical recovery, accuracy and physical interferences were studied. Two of the seven methods are recommended as the most suitable for the purpose.
3-Formyl-BODIPY Phenylhydrazone as a Chromo-Fluorogenic Probe for Selective Detection of NO2 (g)
2016
Anew colorimetric and fluorogenic probe,based on a3-formyl boron dipyrromethene (BODIPY)phe-nylhydrazone, for the sensitive and selectivedetectionNO2(g) has been prepared. The probeinsolution experi-ences aremarkablehypsochromic shift of its absorptionand fluorescence emission bands in the presence gaseousNO2(g), leading to limits of detectio noffew ppb. Theprobe also works in the solid phase, adsorbed on filterpaper strips, or chemically immobilized on the surfaceofsilica nanop articles, with limitsofdetection to the nakedeye of about 0.5 ppm.
Interaction of diazepam with surfactants. Spectrophotometric and spectrofluorometric study
1986
Abstract The interaction of diazepam with non-ionic, anionic and cationic surfactants has been studied spectrophotometrically and fluorometrically. It has been verified that the absorption spectrum of diazepam is not modified in micellar medium. However, a dramatic five-fold increase in fluorescence sensitivity is observed in the presence of sodium lauryl sulphate (SDS). The experimental conditions, temperature, pH and surfactant concentration have been optimized to improve the fluorometric determination of diazepam and a detection limit of 0,04 ppmhas been obtained.
Direct determination of lead in human milk by electrothermal atomic absorption spectrometry
1999
Abstract Infants are particularly sensitive to the toxic effects of lead. Since milk is their only or main food it is important to know the contribution of milk to lead intake. The purpose of this study was to develop a direct method for determining the lead content of human milk by electrothermal atomic absorption spectrometry when a deuterium lamp is the only background correction available. The optimum conditions for lead determination in breast milk: sample dilution in Triton ×-100, modifier (75 μg of palladium) and nitric acid contents (2%) and the graphite furnace program (mineralization: 1100°C; atomization: 2300°C) were selected. The analytical parameters are: linearity (20–300 ng m…
Simultaneous determination of As, Cd, Cr and Pb in aqua regia digests of soils and sediments using electrothermal atomic absorption spectrometry and …
2002
A method was developed for the simultaneous multi-element determination of As, Cd, Cr and Pb in aqua regia digests of soils and sediments using an electrothermal atomic absorption spectrometer with a transversely heated graphite atomizer and longitudinal Zeeman-effect background correction. A fast furnace program with no pyrolysis stage or chemical modifier was used, and the total duration of the time-temperature program of the graphite furnace was 45 s. The method detection limits calculated from blank samples were 9.5 μg l−1, 0.18 μg l−1, 6.2 μg l−1 and 2.5 μg l−1 for As, Cd, Cr and Pb, respectively. Sample preparation procedures are briefly described. The accuracy of the method was confi…
High-performance liquid chromatographic determination of sumatriptan after in vitro transdermal diffusion studies.
2004
A simple, accurate, precise and rapid HPLC method with UV detection has been validated in order to determine the in vitro transdermal absorption of sumatriptan succinate. The HPLC method is a modification of that described by Nozal et al. [M.J. Nozal, J.L. Bernal, L. Toribio, M.T. Martin, F.J. Diez, J. Pharm. Biomed. Anal. 30 (2002) 285-291]. Separation was carried out on a 250 mm Kromasil C18 column at room temperature. The detector response, at 282.7 nm, was found to be linear in a concentration range between 0.145 and 145 microM. The limit of detection (LOD) was 0.019 microM and the limit of quantification (LOQ) was 0.145 microM.