Search results for "Detection limit"
showing 10 items of 810 documents
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.
Low-temperature phosphorescence of 1,4-benzodiazepines
1991
Abstract A highly sensitive method for the low-temperature phosphorescence determination of a series of 1,4-benzodiazepines has been developed. Oxazepam has been used as a test molecule to study the effects of instrumental parameters, such as time decay, gate time, excitation and emission slits, and ordinate, on the phosphorescence spectra. The corresponding analytical parameters have been established for different concentration levels. Under the best sensitivity conditions a limit of detection of 16 parts per trillion (ppt) for oxazepam, 3.8 ppt for medazepam, 2 ppt for prazepam, 5 × 10 −3 ppt for diazepam, and 0.09 ppt for lorazepam could be obtained. The proposed method is thus the most …
Improved technique for quantitative EDXRF analysis of powdered plant samples
1998
An improved technique for energy-dispersive x-ray fluorescence analysis of powdered plant samples is presented. It is based on the use of a special rotating and moveable sample holder (RMSH). This sample holder provides both controlled rotation and lateral transfer movements of the sample while a measurement is carried out, consequently simulating homogeneous excitation conditions over the sample. In this way it compensates for effects caused by the typical inhomogeneous distribution of intensity within the x-ray beam exciting the elements in the sample. The sample consists of powdered dry plant material deposited in an easy way on an adhesive tape, providing a stable layer of plant particl…
Preparation of Hg2+ selective fluorescent chemosensors based on surface modified core–shell aluminosilicate nanoparticles
2010
A synthetic procedure for the preparation of functional structured inorganic–organic hybrid materials consisting of boehmite-silica core–shell nanoparticles and anthracene-containing amines covalently attached to the nanoparticles surface is reported. The system functionalised with the monoamine chain shows a very high sensing performance for Hg2+ detection in pure water reaching a detection limit of 0.2 ppb. Two additional advantages of these systems are their stability over a wide pH window and the feasibility to be recovered by a simple procedure.
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.
Chemiluminescent method for detection of eutrophication sources by estimation of organic amino nitrogen and ammonium in water.
2006
An automatic method has been developed for the estimation of organic amino nitrogen (CH2-NH) and ammonium in water samples. We propose a continuous flow system in which nitrogen compounds react with hypochlorite reagent to produce chloramines. Subsequently, the mixture is mixed with luminol, generating a chemiluminescence signal. The signal emission at 425 nm, registered as a function of time, decreases as nitrogen concentration increases, due to the decrease on hypochlorite concentration. A large number of nitrogen compounds have been assayed and their sensitivities compared, in milligrams per liter nitrogen. The ammonium calibration graph, expressed as N, can be used for most of the assay…
Vibrational Spectrometry Strategies for Quality Control of Procymidone in Pesticide Formulations
2005
Abstract Two vibrational spectrometry–based methodologies were developed for procymidone determination in wettable powdered pesticide formulations. The Fourier‐transform infrared (FTIR) procedure was based on the selective extraction of procymidone by chloroform and determination by peak area measurement between 1451 and 1441 cm−1, using a baseline correction established between 1490 and 1410 cm−1, and a precision of 0.4% and a limit of detection of 0.01% w/w procymidone for a sample mass of 25 mg were obtained. For FT‐Raman determination, the selected conditions were peak area measurement between 1005 and 995 cm−1 Raman shift, with a baseline correction fixed between 1030 and 947 cm−1, and…
Miniaturized matrix solid phase dispersion procedure and solid phase microextraction for the analysis of organochlorinated pesticides and polybromina…
2009
Abstract This work has developed a miniaturized method based on matrix solid phase dispersion (MSPD) using C18 as dispersant and acetonitrile–water as eluting solvent for the analysis of legislated organochlorinated pesticides (OCPs) and polybrominated diphenylethers (PBDEs) in biota samples by GC with electron capture (GC-ECD). The method has compared Florisil®-acidic Silica and C18 as dispersant for samples as well as different solvents. Recovery studies showed that the combination of C18–Florisil® was better when using low amount of samples (0.1 g) and with low volumes of acetonitrile–water (2.6 mL). The use of SPME for extracting the analytes from the solvent mixture before the injectio…
Comparative evaluation of liquid chromatography versus gas chromatography using a β-cyclodextrin stationary phase for the determination of BTEX in oc…
2009
An HPLC method for the determination of benzene, toluene, ethylbenzene and o-xylene, m-xylene and p-xylene in occupational environments was developed and compared with a GC-MS method. Chromatographic analysis using a beta-cyclodextrin stationary phase was performed after active and passive air sampling by adsorption on activated charcoal and pressurized fluid extraction. The analytes were completely separated and quantified using both methods, although GC-MS provided better resolutions and lower detection limits than HPLC. The HPLC method was unsuccessfully applied to the determination of benzene in real samples because its sensitivity was too low. Both methods were applied to the analysis …