Standards Development

Scope

This proposal specifies a method for the determination of free sodium laurate in Sodium lauroyl sarcosinate that is an anionic surfactant used as a foaming and cleansing agent in shampoo, shaving foam, toothpaste, and foam wash products. content of sodium laurate expressed in gram per 100 gram.

Purpose

Sodium Lauroyl Sarcosinate, also known as Sarkosyl, is an anionic surfactant commonly used as a foaming and cleansing agent in products like shampoos, shaving foams, toothpaste, and foam cleansers. Sarcosinates are more soluble in water and less affected by hard water compared to conventional soaps. This mild, biodegradable surfactant is derived from fatty acids and sarcosine (an amino acid). These compounds are known for their lather-building properties and resistance to sebum, making them valuable in cleaners, polymers, industrial chemicals, petroleum products, and lubricants. The presence of the N-methyl amido group [–CON(CH3)–] in the carbon chain significantly influences the physical and chemical properties of the compound

• Unlike traditional soaps, sarcosinates can be incorporated into formulations with a pH as low as 4, achieving excellent results. They generate a generous amount of rich, soap-like foam while remaining mild on the skin. According to Thau, sarcosinates are remarkably compatible with a variety of surfactants, including cationics. They have been shown to strongly adsorb onto various keratin substrates such as skin, hair, and wool within the pH range of 4–7. Sarcosinates exist in equilibrium with small amounts of free N-acyl sarcosinic acid in this pH range. While almost completely solubilized to form clear solutions, the minor amount of free sarcosinic acid exhibits a strong affinity for skin. This makes simple sarcosinate formulations, combined with other mild surfactants such as Sodium Cocoyl Isethionate, ideal for providing a smooth, soft feel on the skin

• Sodium N-lauroyl sarcosinate is produced through the reaction of sarcosine with lauryl chloride. During production, some lauryl chloride reacts with excess alkali, forming sodium laurate, which appears as a by-product in the final product. The sodium laurate content is typically less than 3%. The turbidity and precipitation that can occur when long-chain N-acyl amino acids or their salts are incorporated into liquid detergents—especially when the product is stored at low temperatures (e.g., around 5°C)—are primarily caused by free fatty acids and inorganic salts present in the N-acyl amino acid. These by-products can be carried over from the starting materials or formed during the production process. Notably, free fatty acids can be obtained by the decomposition of the N-acyl amino acid, and once formed, they are difficult to separate from the long-chain N-acyl amino acid or its salts. Therefore, it is crucial to prevent their formation during production.

Advantages of Using Sarcosinate in Formulations:

• Reduced Irritation: Due to the excellent mildness of Sodium Lauroyl Sarcosinate, it can significantly reduce the irritation commonly caused by traditional anionic surfactants such as Sodium Lauryl Sulfate. This makes it suitable for use in baby products and other sensitive skin formulations.

• Foamability: Sodium Lauroyl Sarcosinate is highly effective in a wide range of pH values, offering excellent foamability, making it versatile in many applications.

• Good Sebum Resistance: Unlike many surfactants that have poor resistance to sebum, Sodium Lauroyl Sarcosinate demonstrates superior sebum resistance compared to Sodium Lauryl Sulfate, AOS, SLES, and other surfactants.

The Importance of Determining Sodium Laurate:

• Process Control

• Accurate Calculation of Production Yield

• Accurate Determination of Active Content

• Prevention of Turbidity and Precipitation in Formulations

The active content of sarcosinate is determined using titration methods, and Sodium Laurate can interfere with this titration. To achieve accurate results, it's essential to either separate the lauric acid before titration or account for it in the calculation. Without this step, the active content quantification will not be accurate. 

The analysis of sodium laurate has not been straightforward. Although other analytical methods, including high-performance liquid chromatography and thermo-gravimertic analysis, have been reported in literatures for raw materials and certain mixture of surfactants, this gas chromatographic method combines easy sample preparation and accurate quantitation for the analysis.