I need to analyse anionic surfactants in water but would prefer not to work with chloroform or other carcinogenic reagents.
Any ideas?
Hi.
I would say any other water-imiscible organic solvent. I guess you're using methylene blue, right?
The principle is that methylene blue is a positively charged molecule which will form a neutral complex with anionic compounds such as anionic surfactants. These methylene blue active substances (MBAS) complexes are more soluble in an organic phase than in an aqueous phase. Chloroform is used because it maximizes the MBAS complexes extracted from the aqueous phase, doesn't absorve at the wavelength at which MB does, and is cheap. I would try other solvents on a same standard to test which one will provide the highest signal relatively to a blank after the extraction is done.
Yes, I use MTB and your suggestion makes sense. If you or someone else has experience with using an alternative solvent I would be happy to learn about it , to cut down on in-house method development.
Otherwise could n-butanol be a good starting point? Seem to be transparent >450 nm...
I never tried using an alternative solvent.... sorry.
I forgot to mention earlier that another reason for using chloroform is that it is heavier than water and this facilitates practical operations with the decantation flask.
n-butanol doesn't seem like a good choice because of the difference in polarities, proton donor/acceptor characteristics, density, and solubility in water (around 75g/l at 25 C).
Anyway, you should focus on finding something with a density higher than water and low solubility (< 10 g/L), preferably with similar polarity to chloroform and similar proton donor/acceptor characteristics. Sorry, but besides chlorinated solvents, nothing comes to mind now.
Dear Jesper Knutsson you might find the following links interesting. They are highlighting a different analytical approach. Hope this is of interest. Cheers, Detlef.
https://assets.thermofisher.com/TFS-Assets/CMD/Application-Notes/AN-1080-LC-Linear-Alkylbenzene-Sulfonate-Wastewater-AN70883-EN.pdf
Article Automated Determination of Linear Alkylbenzene Sulphonate (L...
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