Surfactant activity

Studies carried out on anionic, cationic, and nonionic surfactants bave shown tbat tbe aromatic and bydropbilic portions of molecules are easily oxidi2ed, wbereas tbe long hydrocarbon chains are converted at slower rates. Surfactant activity does, however, disappear upon loss of the aromatic portion, thereby reducing the nuisance of the reactants (32). Total mineraLi2ation to CO2 has been demonstrated for nonionic polyethoxylated 4-nonylphenols having average numbers of 2,5, and 12 ethoxy units (33). 

As the example indicates, these liquids contained a complex mixture of surfactant actives. The LAS used in these products was of higher molecular weight (C,2 5-i3 average carbon chain length) than previous laundry liquids. Typical LAS active levels were 12% or less, presumably due to solubility constraints. 

The types of analyses discussed in this section can be divided into two groups active matter and impurities. Several methods assess the anionic surfactant (active matter) content of the AOS product. These are particularly important since detergent performance is directly related to surfactant concentration. The different types of anionic active material are identified and quantified. 

Lung surfactant is composed mainly of lipid with some proteins and carbohydrate and prevents the alveoli from collapsing. Surfactant activity is largely attributed to dipalmitoylphosphatidylcholine, which is synthesized shortly before parturition in full-term infants. Deficiency of lung surfactant in the lungs of many preterm newborns gives rise to respiratory distress syndrome. Administration of either natural or artificial surfactant has been of therapeutic benefit. 

The performance of demulsifiers can be predicted by the relationship between the film pressure of the demulsifier and the normalized area and the solvent properties of the demulsifier [1632]. The surfactant activity of the demulsifier is dependent on the bulk phase behavior of the chemical when dispersed in the crude oil emulsions. This behavior can be monitored by determining the demulsifier pressure-area isotherms for adsorption at the crude oil-water interface. 

TRADE NAME SUPPLIER CHEMICAL FORMULA OF MAJOR SYNTHESISED PRODUCT % SURFACTANT ACTIVITY NATURE OF SURFACTANT COMPOSITION INORGANIC SALT CONTENT/ WATER CONTENT/ ... 

Curstedt T, Hafinan M, Robertson B, et al. 1983. Rabbit lung after long-term exposure to low nickel dust combustion. I. Effects on phospholipid concentration and surfactant activity. Environ Res 30 89-94. 

Surfactant Activity in Micellar Systems. The activities or concentrations of individual surfactant monomers in equilibrium with mixed micelles are the most important quantities predicted by micellar thermodynamic models. These variables often dictate practical performance of surfactant solutions. The monomer concentrations in mixed micellar systems have been measured by ultraf i Itration (I.), dialysis (2), a combination of conductivity and specific ion electrode measurements (3), a method using surface tension of mixtures at and above the CMC <4), gel filtration (5), conductivity (6), specific ion electrode measurements (7), NMR <8), chromatograph c separation of surfactants with a hydrophilic substrate (9> and by application of the Bibbs-Duhem equation to CMC data (iO). Surfactant specific electrodes have been used to measure anionic surfactant activities in single surfactant systems (11.12) and might be useful in mixed systems. ... 

A 100-mL sample aliquot is extracted as above with chloroform. The absorbance of the chloroform solution is read at 652 nm and the amount of anionic surfactants active to methylene blue is determined from the standard calibration... 

FOUND IN Conventional laundry detergents, all-purpose cleaners, and hard-surface cleaners Also known as nonyI phenoxy ethoxylate or nonyl phenol ethoxylate. Researchers in England have found that in trace amounts these synthetic surfactants activate estrogen receptors in cells, which in turn alters the activity of certain genes. For example, in experiments they have been found to stimulate the growth of breast cancer cells and feminize male fish. 

Transmission Electron Microscopy The primary site of surfactant activity appears to be the cell membrane (25, 32). Other effects have been reported such as the denaturation of proteins, inactivation of enzymes and inhibition of mitosis. 

For a compound to be qualified as a surfactant, it should also exhibit surface activity. It means that when the compound is added to a liquid at low concentration, it should be able to adsorb on the surface or interface of the system and reduce the surface or interfacial excess free energy. The surface is a boundary between air and liquid and the interface is a boundary between two immiscible phases (liquid-liquid, liquid-solid and solid-solid). Surface activity is achieved when the number of carbon atoms in the hydrophobic tail is higher than 8 [3]. Surfactant activities are at a maximum if the carbon atoms are between 10 and 18 at which level a surfactant has good but limited solubility in water. If the carbon number is less than 8 or more than 18, surfactant properties become minimal. Below 8, a surfactant is very soluble and above 18, it is insoluble. Thus, the solubility and practical surfactant properties are somewhat related [1]. 

Primary Screening test (648/2 000/EC) Indicator or specific instrumental analysis of surfactant active substances 80% or greater... 

In a study by Consani and Smith, over 140 commercial and commonly available surfactants have been screened for application in CO2 resulting in only a handful with, at best, minute C02-solublilityl2. Recent research in various laboratories, including our own, has developed more soluble surfactants active in CO2 based on the incorporation of C02-philic fluorinated and silicone materialsTT 13-15 Herein we describe the effects of various surfactant and stabilizer systems as they apply to polymerizations in C02-... 

For dilute solutions, surfactant activity equals concentration, and F is calculated from the plot of 7 versus molar concentration. 

Several factors may influence the success or failure of a preservative to protect a formulation against microbial contamination. These factors include the interaction of the preservative with surfactants, active substances, other components of the vehicle, sorption by the polymeric packaging materials, and product storage temperature. Although hundreds of chemicals can fimction as germicides, only a few substances have made it to the marketplace. The small list is not based as much on a compound s effectiveness as an antimicrobial agent as on the compound s safety and effectiveness in the final product. 

When pulmonary surfactant is present in amniotic fluid in sufficient concentrations, the fluid is able to form a highly stable surface film that can support bubbles. Other substances in the fluid, including proteins, bile salts, and salts of free fatty acids, are also capable of forming stable bubbles, but they can be removed from the film by ethanol, which competes with the other substrates for a position in the surface fihn. The test makes use of the principle that more surfactant activity is necessary to support a stable foam as the fraction of ethanol in the mixture is increased. Therefore a fixed volume of undiluted amniotic fluid is mixed with increasing volumes of ethanol, and the largest fraction of ethanol in which the amniotic fluid is stfll capable... 

Simeticone is a silicone derivative its surfactant activity helps to coalesce small gas bubbles into larger ones, which are then vented by eructation. 

The primary reaction of alkali with reservoir water is to reduce the activity of multivalent cations such as calcium and magnesium in oilfield brines. Upon contact of the alkali with these ions, precipitates of calcium and magnesium hydroxide, carbonate, or silicate may form, depending on pH, ion concentrations, temperature, and so on. If properly located, these precipitates can cause diversion of flow within the reservoir, leading to better contact of the injected fluid with the less-permeable and/or less-flooded flow channels. This then may contribute to improved recovery. Also, this reduction of reservoir brine cation activity will lead to more surfactant activity, resulting in lower IFT values (Mayer et al., 1983). 

During emulsification an increase in the interfacial area A takes place and this causes a reduction in T. The equilibrium is restored by the adsorption of surfactant from the bulk, but this takes time (shorter times occur at higher surfactant activity). Thus, e is small whether a is small or large. Because of the lack or slowness of equilibrium with polymeric surfactants, e will not be the same for expansion and compression of the interface. 

In most systems, it is of interest to determine how a change in the alkyl part of the organic molecule (i.e., the hydrophobic part) affects the surface and interfacial tension. In spite of its importance (both in biology and technical industry), no such systematic analysis is found in the current literature. These molecular considerations are pertinent in any reaction where the hydrophobicity might be of major importance in the system, e.g., surfactant activity, EOR, protein structure and activity, and pharmaceutical molecules and activity. 

During the course of reaction, the formation of monoester, owing to its hydrophilicity and surfactant activity, leads to a huge increase in fructose solubility hence, the need for solvent is diminished. In addition, the presence of tert-butanol deters the evaporation of the other esterification product, water. ... 

One of the most widely used indexes for evaluating surfactant activity is the critical micelle concentration (CMC). The CMC is in effect the solubility of a surfactant within an aqueous phase, or the minimum surfactant concentration required for reaching the lowest interfacial or surface tension values y. At concentrations above the CMC, surfactants associate readily to form micelles that can be spherical, oblate, tablet shaped, or rod-like, with a hydrophilic surface and a hydrophobic interior. Such micellar structures usually have hydrodynamic radii, ranging from 200 to 400 A. The CMC value is estimated from the inflection point in the y vs log C curve. 

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