There are not so many published researches concerning the investigation of natural surfactants in oils. Most of them describe HPLC analysis using RC, however the biggest challenge is how to quantify them taking into account the large variety of compounds and low quantity of each of them (only few ppm per each compound). Increasing the injection volume also rises the matrix effect. Even the strategy of such investigation is still unclear. That is why most serious researchers avoid practical investigation, however, there is rising interest to learn the natural surfactants in different natural oils. Another challenge is to separate synthetic surfactants, used by oil companies in EOR processes, from natural ones.
If you are looking to quantify ppm level, I think LC-MS would be a better one.
You may need to do some cleanup and concentration. Depending how polar the surfactant. The routine cleanup procedure I usually use is liquid-liquid extraction between acetonitrile and hexane. Oil will be in hexane and your analyte will be in acetonitrile, concentrate the acetonitrile and go LC using the phase of your choice.
Thank you for concerns. However, from my experience it looks like once the surfactant is in oil, it NEVER leaves it in full. There is always partitioning.
Next challenge is running the phase with some oil traces using LC. Some people recommend to use NC instead of RC. In this case another question arises: which type of column is it better to use?
Need more information, what is the name of the surfactant. The oil is edible oil or crude oil?
Natural surfactants in natural oils, however sometimes people want to analyse synthetic (anionic, like DOWFAX surfactants) surfactants along with natural ones. All surfactants are enough polar. On LC their signals (as well as traces of oil compounds) come together (overlay). LC-MS is an expensive method, so we try to use another, e.g. LC-ELSD instead.
Is it edible oil or crude oil. I have a method for DOSS (surfactant used during the BP oil spill) in seafood.
If you cannot separate it, you may need to dilute and shoot using RP to elute surfactant away from the more non-polar oil which will be retained at a much longer retention time. For sensitivity, use LC/MS.
- Badges
- Science method