Surfactants in shampoos

Cocamidopropyl betaine is the most commonly used amphoteric surfactant in shampoos, bath products, and other cosmetic products. It is popular because of its relatively low irritation potential. 

A characteristic example in the field of cosmetics is the separation and determination of anionic surfactants in shampoos. The sole sample preparation step required is the dilution of the respective product in de-ionized water and membrane-filtration (0.45 pm) prior to injection. Fig. 8-60 illustrates the gradient elution of anionic surfactants in a commercial shampoo with simultaneous conductometric and UV detection. While the peak pattern with UV detection indicates the presence of alkylbenzene sulfonate (ABS) (see also Fig. 5-40 in Section 5.5), the characteristic peak profile for alkylether sulfate (see Fig. 5-39 in Section 5.5) is also evident in the conductometric chromatogram after visually subtracting the ABS-signal. Therefore, application of ion chromatography provides a way to unequivocally identify surfactant raw materials in finished cosmetic products without the time-consuming sample preparation. 

Salts, generally sodium but also triethanolammonium, of long-chain alcohol sulfates and alcohol ether sulfates are the most widely used surfactants in shampoo formulations. Alkanolamides act as viscosity regulators and foam stabilizers. 

The surfactants in shampoos can be classified according to whether or not they carry a charge. With the exception of baby shampoos, most primary surfactants are anionic other surfactants are generally used in a secondary capacity. 

The more complex Lamepon and Igepon type of amides, including the sarcosine (iV-methj lycine) [107-97-1] and A/-methyl taurine (AJ-methylarmno-ethanesulfonate) types shown in Table 4, are used primarily as specialty surfactants in shampoo and toothpaste formulations. These rather complex stmctures have limited use in very specialized applications. 

Generally a carbon chain length of 12 to 14 carbon atoms or a coco-type distribution of approximately 50% Cn is used for the primary surfactant in shampoos because of the excellent foam character and surface-active properties provided by such chain lengths. Longer or shorter chain length surfactants are used only in specialty systems. 

The following table summarizes the most frequently used surfactants in shampoos, along with their advantages and disadvantages. Clearly, no raw material is ideal, and none will meet 100% of... 

Nonionic surfactants, such as fatty ethoxylated alcohols, are rarely used as primary surfactants in shampoos because of their poor foaming properties (Table 6.8). 

Cocamidopropyl betaine (CAPB) is a common secondary surfactant in shampoo formnlations. It improves mildness and viscosity, and enhances the foam properties. It is milder on the skin than linear alkylbenzene sulfonate (LAS), so adding it to the mix reduces the amount of the harsher detergents needed. It is thicker than the other ingredients, so it can be added to make the mix have the right viscosity. It also has antistatic and moisturizing properties. In many shampoos, CAPB is used in combination with sodium lauryl ether sulfate (LES) (Table 6.10). 

Most Frequently Used Surfactants in Shampoo Formulations.158... 

MOST FREQUENTLY USED SURFACTANTS IN SHAMPOO FORMULATIONS... 

Sodinm laureth sulfate or SLES (CAS no. 3088-31-1) is one of the most commonly used anionic surfactants in shampoo formulations. An aqueous concentrated SLES is derived from fatty alcohols, ethoxylated to an average of 2 moles (2EO), and sulfated via a continuous SO3 process. There are a large number of synonyms for SLES available in the literature. Those most frequently cited are provided in Table 8.2 along with strnctnral formula of the surfactant. 

ALS (CAS no. 2235-54-3), a member of the alkyl sulfate group, is also a widely used anionic surfactant in shampoo formulas. The most frequently cited synonyms for ALS in the literature are provided in Table 8.4, along with the structural formula. 

Barker G, Surfactants in shampoos. In Surfactants in Cosmetics, Surfactant Science Series, Vol. 16 (Ed. Rieger MM), Marcel Dekker, New York, 1985, pp. 251-292. 

Donaldson BR and ET Messenger, Performance characteristics and solutions properties of surfactants in shampoos. International Journal Cosmetic Science, 2, 71-90, 1979. 

The foaming properties of protein derivatives are also important features for their use in shampoos. They enable formulators to reduce the level of active surfactants in shampoos without reducing overall foaming power. This becomes of great importance in the formulation of low-active, frequent-use type shampoos where overall foaming effects can still be maintained at low-active levels, minimizing skin and eye irritation. 

A characteristic example in the field of cosmetics is the separation and determination of surfactants in shampoos, which contain various combinations of anionic, cationic, nonionic, and amphoteric surfactants. The surfactant combination is designed to influence the essential characteristics of the shampoo cleansing, foam, conditioning, and viscosity. Laurylether sulfates and alkylben-zene sulfonates are common anionic surfeictants used in shampoos to provide lather and cleansing. The only required sample preparation step is the dilution of the product to be analyzed in deionized water and subsequent membrane filtration (0.45 pm) prior to injection. Figure 10.200 illustrates the gradient... 

This not only applies to shampoos but also to toothpaste, in which anionic surfactants can also be identified, depending on the product. The chromatogram shown in Fig. 9-130 clearly demonstrates that the method developed for the analysis of anionic surfactants in shampoos is also suited for the investigation... 

Sodium alkyl glucoside sulfates containing 10-14 carbon atoms are useful surfactants in shampoos. They were prepared by stirring the appropriate a,/ -glucoside with chlorosulfonic acid in chloroform at 15 °C for 1 hour, followed by neutralization with aqueous sodium hydrogen carbonate. ... 

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