In a Laboratory Practice we teach students how to determine the Critical Micellar Concentration (CMC) of surfactant substances using conductivity measurements. So far we have only used sodium dodecyl sulphate (sodium lauryl sulphate).
You can recommend to me cheap substance, easy to obtain and, if possible with pharmaceutical interest, to carry out such a CMC measure?
Synthesize the sodium salt of stearic acid or soap from stearic acid. This is the most accessible individual surfactant. Students will learn the simple synthesis and definition of CMC. You can get the sodium salt of oleic acid.
For cmc determination we need surfactants with high purity. Therefore its either you synthesise surfactant your own or buy lowgrade surfactants and do recrystallisation.
Thank you very much for your reply. Please can you tell me any specifics or provide me with a bibliographic reference?
Felipe
Kozo Shinoda
The Critical Micelle Concentration of Soap Mixtures (Two-Component) J. Phys. Chem., 1954, 58 (7), pp 541–544 DOI: 10.1021/j150517a007Publication Date: July 1954
Lysolecithin, partially hydrolyzed lecithin of soy origin, seems to be useful for your task.
Dear Dr. Pletnev,
Thank you very much for your reply; do you have any literature you can suggest?
Yours sincerely
Felipe Hernández Luis
Lysolecithin is cheap amphoteric surfactant of medical, food and cosmetic use. Its cmc can be measured by conductometry. Please, see, e.g.:
1. Eugene Hamori, Angela M. Michaels. 1971. Determination of critical micelle concentration of aqueous lysolecithin solutions. Biochim. Biophys. Acta (BBA) - Lipids and Lipid Metabolism 231: 3, 496-504.
2. Richard E. Stafford, Tahsin Fanni, Edward A. Dennis. 1989. Interfacial properties and critical micelle concentration of lysophospholipids. Biochemistry 28: 12, 5113-5120.
Thank you so much for the references. I've requested them from an external database. My university doesn't have them. I'll read them calmly and write to you.
Thank you again
Felipe Hernández Luis
just for demonstration you may use different commercial products starting from hand soap, shampoo, dish washing liquid
.... no literature on this and you demonstrate that there is a critical concentration, you not determine a critical concentration of a particular surfactant, because you have a formulation - but this is practice
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