Isolation and concentration

SolubiHty is used in the refining of oilseed meals to give protein isolates and concentrates (18). Proteins are highly soluble in basic solutions and the... 

Le Bel GL, Williams DT, Griffith G, et al. 1979. Isolation and concentration of organophosphorus pesticides from drinking water at the ng/L level, using macroreticular resin. J AOAC 62 241-249. 

Membrane Ultrafiltration Membrane ultrafiltration is often one of the favored unit operations used for the isolation and concentration of biomolecules because they can be easily scaled up to process large feed volumes at low costs. Toward the end of an ultrafiltration operation, additional water or buffer is added to facilitate the passage of... 

Solid phase extraction (SPE) is a very simple, rapid and reproducible cleanup technique that is now widely accepted as an alternative to the time-consuming liquid-liquid extractions. Additionally, SPE uses relatively small volumes of solvents, and is easy to automate. It is available in a number of different formats, including cartridges, disks, loose material, well plates or SPME using film-coated capillaries. SPE can be considered as an extraction technique when used for isolation and concentration or a cleanup technique when used to remove co-extractives from solvent extracts. The use of SPE for cleanup is discussed later. 

Figure 8.8 is an example of the use of solvent extraction to Isolate and concentrate the insect molting hormone eedysterone... 

Grab samples are usually returned to the laboratory for preconcentration, when required, and analysis [380-384]. Cold trapping techniques are used to Isolate and concentrate the analytes from air prior to separation. Since air contains relatively large volumes of water and carbon - di Bde compared to... 

Isolation and Concentration Techniques Using Physical Methods.739... 

Isolation and Concentration Techn... /aes Using Solvent Extraction. 753... 

The most frequently used methods of analyte isolation and concentration for organic compounds involve distillation, extraction auid adsorption techniques. Some typical applications of these techniques and their attendant -advantages and disadvantages for the analysis of trace organic solutes in water are summarized in Table 8.1 [4,26]. These methods will be elaborated on below and in subsequent sections of this chapter. 

Polyphenols, as one of the largest and most widespread class of plant compounds, are also present in saffron stigma. In the mass spectrum of the flavonoid fraction of the methanolic extract from saffron there were ions at m/z 611 and 633 which may be attributed to protonated and sodiated quasi-molecular ions of kaempferol diglycoside. [22] Flavonoids from the water extract can be isolated and concentrated... 

In a study of the bioaccumulation of metals as colloid complexes and free ions by the marine brown shrimp, Penaeus aztecus [29] the colloids were isolated and concentrated from water obtained from Dickinson Bayou, an inlet of Galveston Bay, Texas, using various filtration and ultrafiltration systems equipped with a spiral-wound 1 kDa cutoff cartridge. The total colloidal organic carbon in the concentrate was found to be 78 lmgdm 3. The shrimps were exposed to metals (Mn, Fe, Co, Zn, Cd, Ag, Sn, Ba and Hg) as radiolabelled colloid complexes, and free-ionic radiotracers using ultrafiltered seawater without radiotracers as controls. The experiments were designed so that the animals were exposed to environmentally realistic metal and colloid concentrations. 

Feeding studies with the rat as the test animal verified the high nutritional quality indicated by the amino acid pattern (45). Using isolates and concentrates prepared from Jewel and Centennial cultivars, PER values were equal to that of casein (milk protein) (Table IV). Examination of the amino acid patterns of sweet potato protein and casein revealed that both contained... 

The solvent sublation procedure of Wickbold [18] is another method that has been used for the analysis of LAS present in seawater [19,20], The solvent sublation technique (gaseous stripping into organic solvent, often ethyl acetate) has also been used to isolate and concentrate nonionic surfactants, e.g. AEs and APEO in aqueous samples [21,22], The co-extracted interferences can be eliminated by cation/anion ion-exchange and alumina chromatography [23,24]. 

Frimer, A. A., J. Org. Chem., 1977, 42, 3194-3196, footnote 7 A new method of preparation involves interaction of ally lie halides in solvents with 98% hydrogen peroxide in presence of silver ion and base at ambient temperature under argon. The reactions must be run in the dark to prevent precipitation of metallic silver, which will catalyse decomposition of the hydroperoxide or excess hydrogen peroxide. In an experiment not run in the dark, the hydroperoxide from 3-chlorocyclohexene ignited spontaneously after isolation and concentration. 

Benomyl was extracted and isolated by the procedure of Austin and Briggs (7). After isolation and concentration, benomyl and its metabolites were determined colorimeCrically. 

The mass spectrometer GC detector has a high degree of compatibility with the purge and trap technique, and GC/MS has been employed widely with this isolation and concentration procedure for the analysis of volatile organic compounds. The mass spectrometer is strongly recommended for samples where there is a possibility of unexpected compounds, and for broad spectrum analyses f 6J of poorly defined samples. 

A sample preparation step aimed at isolating and concentrating the analytes from the matrix is often needed prior to HPLC. Solid samples are usually homogenized with a suitable solvent. Water, acid solutions, saline solutions, or buffers are usually used for peptide extraction from food, but hydro-phobic peptides may require mixtures of chloroform or methylene chloride and methanol. 

Thermal desorption treatment is generally considered to be an alternative to incineration. Thermal desorption operates at much lower temperatures than incineration and keeps the heating systems independent of the wastes, which minimizes off-gas production. The technology can be used as a waste minimization process, isolating and concentrating waste constituents, or as a product recovery process. Thermal desorption can also be used to separate contaminants in mixed waste streams by removing volatile constituents. 

In this paper, we will explore the measurement of and the basis for the cohesive and elastic properties of a commonly used component of foods that excels in these characteristics, wheat gluten. Gluten constitutes from 10 to 16% of wheat flour, from which it may be separated by Martin, batter, or Raisio processes (2, 3). The separated wheat gluten is 70 to 80% protein, of which 85% is insoluble in saline solution. We shall also seek to correlate some of the basic concepts developed in studies of gluten to other protein systems, such as those of soybean protein isolates and concentrates. 

Rapeseed. Methods employed in processing of rapeseed protein products influence emulsion capacities (48, 49). Kodagoda et al. (48) showed that rapeseed protein isolates from water extracts emulsified more oil than isolates from acid or alkali extracts (Table VIII). Rapeseed isolates emulsified more oil than their concentrate counterparts. Rapeseed isolates and concentrates from acid extracts were far superior in emulsion stability to rapeseed protein products from water or alkali extracts. 

Liquid-liquid extraction is used extensively and successfully (6). If the analytes are acidic or basic, as is often the case when HPLC is the analytical method selected, appropriate ionization suppression can be employed to affect the desired extraction. Back extraction of the analytes into an appropriately buffered aqueous volume can then serve to isolate and concentrate. Anionic and cationic surfactants, or so-called ion-pairing reagents, can be added prior to extraction to increase the partition coefficients of the trace organic ionic compounds. 

When comparing the physical and chemical characteristics of natural organics, care should be taken to ascertain that identical methods are used to isolate and concentrate these materials. 

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