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31.
We demonstrate that the selectivity of microchip electrophoresis separations is greatly improved by the presence of organically modified silica (Ormosil) sols in the run buffer. A negatively-charged N-(trimethoxysilylpropyl)ethylenediamine triacetic-acid (TETT)-based sol is used for improving the selectivity between nitroaromatic explosives and a methyltrimethoxysilane (MTMOS)-based sol is employed for enhancing the microchip separation of environmental pollutants, aminophenols. These sols are added to the run buffer and act as pseudostationary phases. Their presence in the run buffer changes the apparent mobility of studied solutes, and leads to a higher resolution. The observed mobilities changes reflect the interactions between the Ormosil sols and the solutes. Relevant experimental variables have been characterized and optimized. The diverse chemistry of Ormosil sols should be extremely useful for tailoring the selectivity of a wide range of electrophoresis microchip separations. 相似文献
32.
This work presents a method to separate polar naphthalenesulfonate (NS) isomers by capillary zone electrophoresis (CZE) with ultraviolet detection in industrial effluents and river water samples. The method involves extraction of samples by a polystyrene‐divinylbenzene copolymer (PS‐DVB) solid‐phase extraction (SPE) cartridge. The most effective CZE separation conditions were obtained in 20 mM borate buffer with 30% acetonitrile at pH 9.0 and 30 °C. The method proposed herein provides a high precision and sensitivity for NS isomers, to quantitation at ≤ 1.0 μg/L in 200 mL of the water samples. Recovery of the NS isomers in spiked water samples ranged from 73% to 87% while RSD ranging from 5.6 to 9.7%. The analysis of industrial effluents and river water samples was performed and naphthalene‐2‐sulfonate was found as a major pollutant. The difficulties in quantitating and identifying analytes in complex environmental samples can be resolved by using an internal standard response factor to calculate concentrations and relative migration times for peak confirmation. 相似文献
33.
V. Bruder-Hubscher F. LagardeM.J.F. Leroy C. CoughanowrF. Enguehard 《Analytica chimica acta》2002,451(2):285-295
The release of five elements (Cr, Cu, Mn, Pb and Zn) from a municipal solid waste incineration bottom ash (BA) under different extraction conditions has been investigated by performing the three-step sequential extraction procedure proposed by the Standards, Measurements and Testing Program of the European Union. A fourth step (strong acid attack) has been added in order to calculate the mass balance. The results of this study provide information on the potential mobility of the studied elements. Almost all of the Cr and part of the Mn are extracted with strong acid which indicates low potential mobility in the environment. Most of the Cu is extracted under oxidizing conditions. Pb and Zn are released under acidic condition, indicating the possibility of their mobilization by changes in pH. The reproducibility of the sequential extraction procedure is also discussed. 相似文献
34.
A simple and effective method is presented for the separation and preconcentration of thorium(IV) and uranium(VI) by solid phase extraction on Duolite XAD761 adsorption resin. Thorium(IV) and uranium(VI) 9-phenyl-3-fluorone chelates are formed and adsorbed onto the Duolite XAD761. Thorium(IV) and uranium(VI) are quantitatively eluted with 2 mol L−1 HCl and determined by inductively coupled plasma-mass spectrometry (ICP-MS). The influences of analytical parameters including pH, amount of reagents, amount of Duolite XAD761 and sample volume, etc. were investigated on the recovery of analyte ions. The interference of a large number of anions and cations has been studied and the optimized conditions developed have been utilized for the trace determination of uranium and thorium. A preconcentration factor of 30 for uranium and thorium was achieved. The relative standard deviation (N = 10) was 2.3% for uranium and 4.5% for thorium ions for 10 replicate determinations in the solution containing 0.5 μg of uranium and thorium. The three sigma detection limits (N = 15) for thorium(IV) and uranium(VI) ions were found to be 4.5 and 6.3 ng L−1, respectively. The developed solid phase extraction method was successively utilized for the determination of traces thorium(IV) and uranium(VI) in environmental samples by ICP-MS. 相似文献
35.
V. Pichon H. Rogniaux N. Fischer-Durand S. Ben Rejeb F. Le Goffic M. -C. Hennion 《Chromatographia》1997,45(1):289-295
Summary The trace-level determination of organic pollutants in complex matrices is difficult and often not reliable because theccurrent
extraction procedures are non-selective. New extraction sorbents involving antigen-antibody interactions, called immunosorbents
(ISs), have been synthesised in order to trap a group of structurally related pollutants. The IS capacity is always high for
the analyte-antigen used to make the antibodies, but can be low for some related compounds. In this work, we show the relationship
that exists between capacity, break-through volume and recovery of analytes because of the competition between the structurally
related compounds for antibody sites. Breakthrough due to the overloading of the column should be avoided because calibration
curves are no longer linear. The capacity of two ISs, one made for trapping the triazine pesticide group and the second for
the phenylurea, group, have been optimised by selecting silica with 50 nm pore size. Calibration curves are linear for all
the compounds in a mixture of ten phenylureas up to a concentration of 5 to 10 μg L−1 for each compound when handling 50 mL water samples through a precolumn packed with 0.22 g of IS. Under these conditions,
reliable quantitative results are obtained because calibration curves are similar when compounds are alone or in a mixture.
Application to the clean-up of soil extracts illustrates the high selectivity and the high potential of these new sorbents
in environmental analysis.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
36.
Summary A method has been developed for the determination of trace levels of 32 pesticides, 19 explosives and 16 polycyclic aromatic
hydrocarbons (PAH) in water in three individual steps. Solid-phase enrichment (SPE) is coupled to high-performance liquid
chromatography (HPLC) with a fully automated system. The organic pollutants are enriched on reusable cartridges packed with
adsorbent materials: pesticides and explosives on a mixed bed of divinylbenzene-ethylvinylbenzene copolymers (LiChrolut EN?) and perfluorinated polyethylene (PolyF?), and polycyclic aromatic hydrocarbons on C18-modified silica (Zorbax? ODS1). Thermally assisted desorption (TAD) has been shown to increase the recovery of analytes significantly. As all enriched
analytes are transferred to the detector, only fifty millilitres of sample is needed for each single on-line analysis, compared
with at least a litre for conventional methods. The separation of the enriched organic analytes is performed on specialized
HPLC columns based on reversed-phase materials. The limits of detection of the system employed were found to be below 100
ng L−1. Use of fluorescence detection for the polycyclic aromatic hydrocarbons resulted in limits of detection in the upper pg L−1 range. Thek values, number of theoretical plates, the recovery rates and the limits of detection of this method for fast screening of
organic pollutants from three fifty-millilitre aqueous samples are described.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
37.
Margaret Sequeira Dermot Diamond Antoine Daridon Jan Lichtenberg Sabeth Verpoorte N. F. de Rooij 《Trends in analytical chemistry : TRAC》2002,21(12):816-827
Progress in the development of a micro-fluidic system for colorimetric monitoring of ammonia in drinking and wastewater is described. The ultimate goal is to have a miniaturised instrument that can produce accurate, reliable measurements, is easy to operate, has minimal power consumption, and can operate autonomously for a year. In this study, the indophenol reaction is incorporated into a simple, reliable analytical micro-fluidic system. Absorbance measurements for the blue ammonia-indophenol complex formed in the micro-fluidic system are shown. A key issue is the limiting stability of hypochlorite, a reagent used in the assay. The effects of hypochlorite concentration and impurities on the stability of hypochlorite are investigated and discussed. Decomposition is shown to be very dependent on the presence of heavy-metal impurities. With low levels of these catalytic metals and careful storage, hypochlorite has been shown to be stable for over a year. 相似文献
38.
A homologous series of 2,4-dichlorobenzyl alkyl ethers (DCBEs) have been synthesized and purified for use as retention index calibrants and internal standards. They are stable, sensitive to ECD and FID and ideal for GC-MS, with base peaks at m/z 159/161. The retention index calibration against the n-alkanes for a linear temperature program (LTP) series is given and recommendations made for the most suitable members of the DCBE series for use as internal standards in organochlorine (OC) residue analysis. 相似文献
39.
Karlheinz Ballschmiter 《Angewandte Chemie (International ed. in English)》1992,31(5):487-515
The role of chemistry in our soon-to-be global industrial society requires a global perspective for the discussion of the uptake, transport, and conversion of chemical compounds in the environment. The fate of organic compounds in the volume flow of the atmosphere and hydrosphere can be categorized into transport pathways and adjustments of equilibria in the multiphase system atmosphere-oceans-land surface. The global volume flow in the atmosphere (wind, areas of high and low pressure) and in the hydrosphere (rivers, circulation of water in lakes, ocean currents) alone would account for the transport of organic compounds if they were stable and if all these compounds were molecularly distributed in these phases. However, this particular case is observed only for volatile chlorofluorocarbons and tetrachloromethane. For most organic compounds, complex adsorption/desorption processes on finely dispersed particle phases in the air and water as well as abiotic and biotic transformations determine the transport behavior. The global fate of a compound includes its accumulation as well as its decomposition in defined environmental compartments. Both phenomenon may have long-term consequences in the af-fected areas; this is indicated by the accumulation of polychlorobiphenyls and analogous compounds in marine mammals and deep-sea fauna, and is evident in the decomposition of chlorofluorocarbons in the stratosphere. The accepted definition of the level of a risk, the product of the probability of an event and the potential amount of damage, takes on a new dimension when viewed from a global perspective-especially when one further connects the extent of the damage to the possible means of correction. It is the responsibility of scientists to point out the irreparable regional to global consequences directly and indirectly connected to the production of chemicals and to provide suggestions for prevention. Politicians can only react by applying their methods to limit the damage; however, they cannot generate any solutions based on science. 相似文献
40.
Summary A preliminary study has been carried out to evaluate a new adsorbent, Thermosorb, for trace level organic contaminants. For this purpose, a comparison was made with a well-characterized adsorbent, Tenax GC, using a prepared aqueous solution of trace organic components. In addition, a comparison was made of chromatograms of air contaminants obtained using both of these adsorbents, under equivalent conditions. The results clearly indicated the potential of this thermally stable, inorganic adsorbent for many trace organic substances of environmental interest. 相似文献