Labelling of surfactants

For safety assessment of surfactants a CESIO Committee has published a proposal for the labeling of surfactants [254]. The conclusions for ether carboxylates based on the then-available Figures are given in Table 16. 

Classification and Labelling of Surfactants, CESIO Report, 12 October 1990. 

CESIO Recommendation for the Classification and Labelling of Surfactants as Dangerous for the Environment , April 2003. 

Many benzenoid quaternary cationic surfactants possess germicidal, fungicidal, or algicidal activity. Solutions of such compounds, alone or in combination with nonionic surfactants, are used as detergent sanitizers in hospital maintenance. Classified as biocidal products, their labeling is regulated by the U.S. EPA. The 1993 U.S. shipments of cationic surfactants represented 16% of the total sales value of surfactant production. Some of this production is used for the preparation of more highly substituted derivatives (101). 

The change in properties of solutions of surfactants at CMC shown below in the diagram as 1, 2, 3. Labelled ... 

Dividing both sides of Equation (8) by n expresses this free energy change per mole of surfactant we shall label this AG, .. At the CMC, aM as = aCMC, so per mole of surfactant, Equation (8) becomes... 

A portion of the wet sol-intercalated clay was mixed with a surfactant of quaternary ammonium salts [CH3(CH2)n-i N(CH3)3Br] by stirring for 2 hours. 15.75 mmol of surfactant was added to each gram of the starting bentonite clay. The resultant mixture of clay and surfactant was transferred into an autoclave and kept in an oven at 100°C for 3 days. The wet cake was washed with water to Cl ions free and the solid was recovered by filtration. The solid was dried in room temperature and calcined at 773 K. for 4 h. The calcined products were labeled as sol-PILB-Cn, where n denotes the number of carbon atoms in the alkyl chain of the surfactants used. Four samples were prepared sol-PILB-C12, -C14, -C16 and -C18. 

Adsorption can be measured by direct or indirect methods. Direct methods include surface microtome method [46], foam generation method [47] and radio-labelled surfactant adsorption method [48]. These direct methods have several disadvantages. Hence, the amount of surfactant adsorbed per unit area of interface (T) at surface saturation is mostly determined by indirect methods namely surface and interfacial tension measurements along with the application of Gibbs adsorption equations (see Section 2.2.3 and Figure 2.1). Surfactant structure, presence of electrolyte, nature of non-polar liquid and temperature significantly affect the T value. The T values and the area occupied per surfactant molecule at water-air and water-hydrocarbon interfaces for several anionic, cationic, non-ionic and amphoteric surfactants can be found in Chapter 2 of [2]. 

In 1993, the European Union revised its criteria for classification and labelling of substances and preparations based on their potential to cause ocular lesions [5] and in 1995 new experimental data on the irritation potential of surfactant raw materials became available. This led CESIO, once again, to review its guidance on classification and labelling of anionic and non-ionic surfactants. It resulted in the increase in several classification and labelling recommendations. These revisions, together with the classifications for quaternary ammonium compounds and fatty amines and derivatives which remained unchanged from the 1990 Report, are contained in the latest report published in January 2000 [6]. 

Penfold et al. [62] have also used neutron reflectivity to study the adsorption (structure and composition) of the mixed anionic/nonionic surfactants of SDS and C12E6 at the hydrophilic silica-solution interface. This is rather different case to the cationic/nonionic mixtures, as the anionic SDS has no affinity for the anionic silica surface in the absence of the Ci2E6. The neutron reflectivity measurements, made by changing the isotopic labelling of the two surfactants and the solvent, show that SDS is coadsorbed at the interface in the presence of the Ci2E6 nonionic surfactant. The variations in the adsorbed amount, composition, and the structure of the adsorbed bilayer reflect the very different affinities of the two surfactants for the surface. This is shown in Fig. 7, where the adsorbed amount and composition is plotted as a function of the solution composition. 

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