Enrichment methods, isolation

Selected enrichment and isolation methods of surfactants in wastewater (WW), coastal water (CW), estuarine water (EW), surface water (SW), ground water (GW) and drinking water (DW) matrices with adjacent LC-separation detection by MS, UV and FL... 

Liquid chromatography cleanup on a LiChrosorb Diol column has been further proposed for the offline purification of chloramphenicol residues from bovine muscle and eggs (32). An online approach based on reversed-phase principles has also been described for isolation of chloramphenicol residues from swine kidney by an automated column switching system (63). Use of a protein exclusion column (Hisep) has been also suggested in an online trace-enrichment method for the determination of chloramphenicol in animal tissues (52). By employing a column-switching system, all chloramphenicol that eluted from the protein exclusion column was trapped at the entry of a 5 m Supelcosil LC-18 preconcentration column, to be subsequently back-flashed into the analytical column. 

It has been suggested that all the gram positive bacteria may have descended from photosynthetic ancestors and indeed that the ancestor of all eubacteria was photosynthetic (5). It is, therefore, important to search for other new types of photosynthetic bacteria in an effort to shed more light on the early evolution of photosynthesis. Our findings suggest that such organisms may not be ubiquitous and will require specific enrichment methods for their isolation. REFERENCES... 

Silver-ion chromatography can be a useful technique for isolation of a fraction enriched in CLA, but it can also afford unrivaled analytical separations. Silver-ion thin-layer chromatography (TLC) is best regarded as an enrichment method. With a mobile phase such as hexane/diethyl ether (9 1, vol/vol), CLA as the methyl ester elutes with cis-monoenes, rather than with a diene fraction with toluene as mobile phase, it elutes just ahead of the cw-monoenes (10). Alternatively, solid-phase extraction columns with bonded sulfonic acid moieties converted to the silver-ion form can be used with a simple elution scheme to obtain a combined monoene-CLA fraction (2,11). 

Various strategies have been developed for the enrichment of microbial samples. The enrichment methods involving non-covalent, covalent interactions, and immunoassays are discussed in this section. In general, affinity enrichment steps include binding of targets, washing, and elution. A general scheme is provided in Fig. 3.2. Microbial cells/markers are isolated and concentrated after the incubation of the sample solution with affinity probes. The enriched cells are lysed or directly mixed with a matrix-assisted laser desorption/ionization (MALDI) matrix solution and subjected to mass spectrometry (MS) analysis. Moreover, biomarkers obtained from the enriched cells may be concentrated and separated prior to MS analysis... 

A multiresidue analytical method based on sohd-phase extraction enrichment combined with ce has been reported to isolate, recover, and quantitate three sulfonylurea herbicides (chlorsulfuron, chlorimuron, and metasulfuron) from soil samples (105). Optimi2ation for ce separation was achieved using an overlapping resolution map scheme. The recovery of each herbicide was >80% and the limit of detection was 10 ppb (see Soil chemistry of pesticides). 

There are different ways, both passive and active, to provide this desired protection against deflagrations and detonations. Methods inclnde DBAs, venting, pressnre containment, oxidant concentration rednction (inerting and fnel enrichment), combnstibles concentration rednction (ventilation or air dilntion), deflagration snppression, and eqnipment and piping isolation. These are discnssed in more detail in Chapter 3. 

The only respect in which the hot atom chemistry of organometallic compounds has so far been applied to other fields of study is in the area of isotope enrichment. Much of this has been done for isolation of radioactive nuclides from other radioactive species for the purpose of nuclear chemical study, or for the preparation of high specific activity radioactive tracers. Some examples of these applications have been given in Table II. The most serious difficulty with preparation of carrier-free tracers by this method is that of radiolysis of the target compound, which can be severe under conditions suited to commercial isotope production, so that the radiolysis products dilute the enriched isotopes. A balance can be struck in some cases, however, between high yield and high specific activity (19, 7J),... 

Maltseva O, P Oriel (1997) Monitoring of an alkaline 2,4,6-trichlorophenol-degrading enrichment culture by DNA fingerprinting methods and isolation of the responsible organism, haloalkaliphilic Nocardioides sp. strain M6. Appl Environ Microbiol 63 4145-4149. 

Widdel F (1983) Methods for enrichment and pure culture isolation of filamentous gliding sulfate-reducing bacteria. Arch Microbiol 134 282-285. 

K. Alef, Enrichment, isolation and counting of. soil microorganisms. Methods in Applied Soil Microbiology and Biochemistry (K. Alef, P. Nannipieri, eds.). Academic Press, New York, 1995, p. 123. 

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