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171.
A new reversed-phase liquid chromatograhy/electrospray ionization tandem mass spectrometry method was developed for the analysis of perchlorate in water. The improved separation of perchlorate from common anions along with sample dilution effectively reduced matrix effects, primarily ion suppression caused by common anions. The (18)O-enriched perchlorate used as an internal standard provided further compensation for potential changes associated with instrument sensitivity, retention time shifting, peak broadening, ion suppression, and other matrix effects. The mean recoveries and relative standard deviations were 92-107% and 2.5-9.5% for simulated water matrix spikes at 0.05-1.0 microg/L, and 80-106% and 3.8-13% for real water sample matrix spikes at 2.0 microg/L, respectively. The method detection limits were 0.007 microg/L for reagent water and 0.014 microg/L for the simulated water matrix that contained 100 mg/L of SO(4)(2-), CO(3)(2-), and Cl(-) anions; 2 mg/L of PO(4)(3-) as P and NO(3)(-) as N; and 0.1 mg/L of Br(-), BrO(3)(-), ClO(2)(-), ClO(3)(-), and F(-) anions in reagent water, respectively. When using cartridge pretreatment to remove problematic SO(4)(2-), CO(3)(2-), and Cl(-) anions, the minimum reporting level could be set to 0.05 microg/L or lower. With 10-fold dilution, the minimum reporting level was conservatively set to 0.5 microg/L. 相似文献
172.
Analytical methods for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are widely available
and are the result of a vast amount of environmental analytical method development and research on persistent organic pollutants
(POPs) over the past 30–40 years. This review summarizes procedures and examines new approaches for extraction, isolation,
identification and quantification of individual congeners/isomers of the PCBs and OCPs. Critical to the successful application
of this methodology is the collection, preparation, and storage of samples, as well as specific quality control and reporting
criteria, and therefore these are also discussed. With the signing of the Stockholm convention on POPs and the development
of global monitoring programs, there is an increased need for laboratories in developing countries to determine PCBs and OCPs.
Thus, while this review attempts to summarize the current best practices for analysis of PCBs and OCPs, a major focus is the
need for low-cost methods that can be easily implemented in developing countries. A “performance based” process is described
whereby individual laboratories can adapt methods best suited to their situations. Access to modern capillary gas chromatography
(GC) equipment with either electron capture or low-resolution mass spectrometry (MS) detection to separate and quantify OCP/PCBs
is essential. However, screening of samples, especially in areas of known use of OCPs or PCBs, could be accomplished with
bioanalytical methods such as specific commercially available enzyme-linked immunoabsorbent assays and thus this topic is
also reviewed. New analytical techniques such two-dimensional GC (2D-GC) and “fast GC” using GC–ECD may be well-suited for
broader use in routine PCB/OCP analysis in the near future given their relatively low costs and ability to provide high-resolution
separations of PCB/OCPs. Procedures with low environmental impact (SPME, microscale, low solvent use, etc.) are increasingly
being used and may be particularly suited to developing countries.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
173.
174.
175.
176.
Ohne Zusammenfassung 相似文献
177.
Raphael Ed. Liesegang 《Colloid and polymer science》1922,31(2):110-111
Ohne Zusammenfassung 相似文献
178.
Steingrimsson’s coloring complex and Jonsson’s unipolar complex are interpreted in terms of hyperplane arrangements. This
viewpoint leads to short proofs that all coloring complexes and a large class of unipolar complexes have convex ear decompositions.
These convex ear decompositions impose strong new restrictions on the chromatic polynomials of all finite graphs. Similar
results are obtained for characteristic polynomials of submatroids of type ℬ
n
arrangements.
The first author was supported by NSF grant DMS-0500638. The second author was supported by NSF grant DMS-0245623. 相似文献
179.
William Blum R. S. Mc Bride H. F. V. Little F. J. Metzger R. F. Mc Crackan E. Deiss Ed. Donath W. Heike M. Huybrechts N. Joassart S. Crook U. S. Stahlverbandes T. C. Waters P. Slawik H. B. Swan J. R. Huber E. Müller P. Koppe L. E. Marrs Emm PozziEscot M. Dittrich W. Cornelius W. Dederichs und F. H. Campbell 《Fresenius' Journal of Analytical Chemistry》1914,53(4-5):282-300
Ohne Zusammenfassung 相似文献
180.
Raphael Ed. Liesegang 《Colloid and polymer science》1912,10(5):225-232
Ohne ZusammenfassungNeurologisches Institut Frankfurt am Main, Dir. L. Edinger. 相似文献