Surfactants as wetting agent

Florence (1983) provide a comprehensive reference for the use of surfactants in drug formulation development. The treatment by Florence (1981) of drug solubilization in surfactant systems is more focused on the question at hand and provides a clear description of surfactant behavior and solubilization in conventional hydrocarbon-based surfactants, especially nonionic surfactants. This chapter will discuss the conventional surfactant micelles in general as well as update the reader on recent practical/commercial solubilization applications utilizing surfactants. Other uses of surfactants as wetting agents, emulsiLers, and surface modiLers, and for other pharmaceutical applications are nc emphasized. Readers can refer to other chapters in this book for details on these uses of surfactant Polymeric surfactant micelles will be discussed in Chapter 13, Micellization and Drug Solubility Enhancement Part II Polymeric Micelles. 

USE Sodium salt as pharmaceutic aid (surfactant) as wetting agent in industrial, pharmaceutical, cosmetic and food applications dispersing and solubilizing agent in foods adjuvant in tablet formation. 

The sodium salts of the ether sulfates have relatively limited water solubility. They seldom perform as well as do many other anionic surfactants as wetting agents, but their foaming properties are considerably better. They have found extensive use in shampoo formulations, and, in combination with other anionic and nonionic surfactants, they are being used more for household dishwashing detergents. 

All lnaphthalenesulfonic Acids. The aLkyLnaphthalenesulfonic acids can be made by sulfonation of aLkyLnaphthalenes, eg, with sulfuric acid at 160°C, or by alkylation of naphthalenesulfonic acids with alcohols or olefins. These products, as the acids or their sodium salts, are commercially important as textile auxiUaries, surfactants (qv), wetting agents, dispersants (qv), and emulsifying aids, eg, for dyes (qv), wettable powder pesticides, tars, clays (qv), and hydrotropes. 

It is sometimes possible to add properties in Hquid formulations that provide additional functions. Examples in development or in commercial use as of 1993 include microencapsulation (qv) of enzymes for protection against bleach when dispersed in a Hquid detergent addition of certain polymers to protect the enzyme after it has been added to Hquid detergents (32), or to boost activity in the final appHcation addition of surfactants or wetting agents. 

Surfactants are often used in agrochemical formulations as adjuvants, e.g. as wetting agents to improve the physico-chemical characteristics of the solution and to increase the uptake of active ingredients (e.g. pesticides) [6-8]. The surfactants can be included in pesticide products and/or added to the tank mix prior to use however, they rarely exceed 1% of the total applied spray. Examples of typical surfactants used in agrochemical formulations are shown in Table 2.8.3 [9]. 

The influence of the oil type and quality on oil absorption and residues absorbed by fried foods is widely documented (e.g., Blumenthal, 1991 Blumenthal and Stier, 1991 Krokida et al., 2000 Nonaka et al, 1977 Pokomy, 1980). No relationship has been found between oil type and oil absorption however, it has been shown that an increase in the initial interfacial tension between oil and restructured potato products decreases oil absorption (Pinthus and Saguy, 1994). Further, as mentioned earlier, oil degradation produces surfactants that act as wetting agents, which also increase the absorption (Blumenthal, 1991). 

Surfactants, emulsifiers Dissolve lipids, disrupt membranes, denature proteins, and inactivate enzymes in high concentrations, and act as wetting agents Cationic detergents are used to sanitize utensils, anionic detergents are used to launder clothes and clean household objects, and quaternary ammonium compounds are sometimes used as an antiseptic on skin... 

Surfactants have the property of adsorbing strongly on hydrophobic particle surfaces. They consist of a hydrophilic polar head such as -(CH2CH20)n0H, -0S02Na+, -N+(CH3 )2 (CH2 )2 S03 and a hydrophobic tail (i.e., linear or branched hydrocarbon chain). The hydrophobic tail adsorbs on the hydrophobic particle surfaces while the hydrophilic head sticks out toward water. The particles are thus hydrated. Surfactants with a hydrophilic/lipophilic balance (HLB) (see Section 4.2) value close to 7 to 9 are well suited as wetting agents. These surfactants form monolayers on the solid surface. 

Aqueous suspensions comprise a wide range of adhesives. These will contain as additives the various soaps, surfactants, and wetting agents necessary to stabilize the emulsion or latex. Additives are also incorporated into aqueous formulations to provide system stability under repeated freeze-thaw cycles during storage. 

Surfactants act as wetting agents by lowering the surface tension of the waterborne epoxy. Silanes can be used to increase adhesion to certain substrates and fillers, as shown in Table 14.4, formulation C. Water-compatible thickeners and protective colloids such as polyvinyl alcohol, substituted cellulosics and sugars, and some acrylics improve application properties and offset viscosity decrease seen with water dilution. 

The ability of soap to help wet a surface makes it a good surfactant or wetting agent . The major problem with soap is that, with any calcium ions present, as in... 

The irradiation of micellar solutions effects the phase behavior and the critical micelle concentration (CMC). Because radiation sterilization of biopharmaceutical products is a common routine it is important to investigate the influence of radiation on surfactants that are widely used in the pharmaceutical industry for formulations as wetting agents, emulsifiers, or solubilizers. In particular, in drug formulations... 

Surfactant Substance that adsorbs to surfaces or interfaces to reduce surface or interfacial tension may be used as wetting agent, detergent, or emulsifying agents Benzalkonium chloride, nonoxynol 10, oxtoxynol 9, polysorbate 80, sodium lauryl sulfate, sorbitan monopalmitate... 

In dyeing, surfactants are used as wetting agents. They are also used in the formulation of disperse dyes. A stable suspension of the dye is prepared with the help of an anionic surfactant, such as alkyl or aryl alkyl sulfonate. It has been shown that dyeing takes place through the aqueous phase by the slow dissolution of the solid dye particles (61, 62). The presence of the surfactant helps the dissolution of the dye. 

The adsorption of surfactants onto solid surfaces is important with respect to their detergent properties, their use as wetting agents in solid pharmaceutical dosage forms, and as stabilizers for suspension formulations. The mode of action of surfactants in each of these systems is discussed further below. 

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