High molecular weight compounds

Attempts to characterize polymeric substances had been made, of course, and high molecular weights were indicated, even if they were not too accurate. Early workers tended to be more suspicious of the interpretation of the colliga-tive properties of polymeric solutions than to accept the possibility of high molecular weight compounds. Faraday had already arrived at Cs Hg as the empirical formula of rubber in 1826, and isoprene was identified as the product... 

Both the m- and -phenylenediamines are used to manufacture sulfur dyes, either by refluxing in aqueous sodium polysulfide, or heating with elementary sulfur at 330°C to give the leuco form of the dye. These dyes are polymeric, high molecular weight compounds, and soluble in base. The color is developed by oxidation on the fabric. 2,4-Toluenediamine and sulfur give Sulfur Orange 1 (14). 

Aliphatic acids or esters Mostly high-molecular-weight compounds diethyl phthalate laiiric acid Papermaking wood-pulp suspensions water-based paints food processing... 

Enantioresolution in capillary electrophoresis (CE) is typically achieved with the help of chiral additives dissolved in the background electrolyte. A number of low as well as high molecular weight compounds such as proteins, antibiotics, crown ethers, and cyclodextrins have already been tested and optimized. Since the mechanism of retention and resolution remains ambiguous, the selection of an additive best suited for the specific separation relies on the one-at-a-time testing of each individual compound, a tedious process at best. Obviously, the use of a mixed library of chiral additives combined with an efficient deconvolution strategy has the potential to accelerate this selection. 

Chelants are relatively high molecular weight compounds and react stoichiometrically with cations. In higher hardness waters the consumption of chelant-based programs may be both excessive and expensive consequently, they are not normally employed with high hardness FW sources. 

The pH of the solution is also of critical importance, not only in terms of whether or not ionization occurs, but also, particularly in the case of high-molecular-weight compounds, the appearance of the spectrum (see Section 4.7.3 below). The production of positive ions is favoured at acidic pH but ions have... 

If a high -molecular-weight compound is being studied by LC-MS, the analyst has little choice in the ionization method to use, with atmospheric-pressure chemical ionization (APCl) being wholly inappropriate. However, when low -molecular-weight componnds are involved, both electrospray ionization and APCl are potentially of value. 

Matrix-assisted laser desorption ionization (MALDI) A method used for the ionization of high-molecular-weight compounds. In this approach, the analyte is crystallized with a solid matrix and then bombarded with a laser of a frequency which is absorbed by the matrix material. 

Polymerisation involves the chemical combination of a number of identical or similar molecules to form a complex molecule. The resulting polymer has a high molecular weight. The term synthetic polymer is usually employed to denote these compounds of very high molecular weight. Compounds which polymerise include ... 

Exudate collection in trap solutions usually requires subsequent concentration steps (vacuum evaporation, lyophilization) due to the low concentration of exudate compounds. Depending on the composition of the trap solution, the reduction of sample volume can lead to high salt concentrations, which may interfere with subsequent analysis or may even cause irreversible precipitation of certain exudate compounds (e.g., Ca-citrate, Ca-oxalate, proteins). Therefore, if possible, removal of interfering salts by use of ion exchange resins prior to sample concentration is recommended. Alternatively, solid-phase extraction techniques may be employed for enrichment of exudate compounds from the diluted trap solution (11,22). High-molecular-weight compounds may be concentrated by precipitation with organic solvents [methanol, ethanol, acetone 80% (v/v) for polysaccharides and proteins] or acidification [trichloroacetic acid 10% (w/v), per-... 

Within the reactor, however, 6 per cent of the n-butyraldehyde product is reduced to n-butanol, 4 per cent of the isobutyraldehyde product is reduced to isobutanol, and other reactions occur to a small extent yielding high molecular weight compounds (heavy ends) to the extent of 1 per cent by weight of the butyraldehyde/butanol mixture at the reactor exit. 

Advantages Easier to produce than reservoir devices Can deliver high molecular weight compounds... 

Because wax and lipid substances may contain high molecular constituents, a first run is usually performed with a scan range from m/z 50 to 900 or 1000. In a second step, if the mass spectrum excludes the presence of high molecular weight compounds, and if enough matter is available for analysis, another run is performed over a narrower scan range, often between m/z 50 and 500 (Colombini et al., 2005b). 

Most phenols are relatively high-molecular weight compounds with large nonpolar portions and therefore, they exhibit low solubilities in water. ... 

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