You can form an emulsion with just one surfactant. Using two surfactants in many cases will lead to greater stability

It depends on the surfactant. Some surfactants are more easily dissolved in water and some are more easily dissolved in oil. Dissolve the surfactant in the phase in which it is more soluble

To get an emulsion you just need to supply the energy (mix it energetically). However if you want particular properties such as droplet size, stability etc these wil vary with the system you use and the amount of energy you put into mixing the system. In this case you would be wise to look up the details of systems that people have studied carefully.

It's not clear to me what the relationship between your emulsion questions is to spray drying

Hi Vincent,

Its just I will be subjecting the emulsion to spray drying. haha

Based on my own observation, Tween 80 seems to be able to dissolve alright in both water and oil.

So it doesn't matter where I dissolve the surfactant?

I can just dissolve it in water before any addition of any material?Or after I dissolve maltodextrin in water?Or even at the end after adding Oil into aqueous phase?

There is no fix steps or procedure to follow?

Olivia, As long as you can get the surfactant to dissolve it is unlikely that the order of addition matters. In the end the surfactant will partition between the the water, oil and the interface. There is a chance that the surfactant and the maltodextrn might interact strongly (ulikely) so I suggest putting the surfactant in the oil phase and the maltodextrin in the aqueous phase, putting them together and then mixing. With a lot of formulation work it is worth just trying it on a small quantity first and seeing what happens. The more components the harder it is to predict what will happen.

Hi Vincent,

Thanks..that helps alot..I was wondering if the order of addition of surfactants actually matters.

But what if I am using Tween 80 and Span 20.

Is it advisable for Tween to be in Oil phase and Span to be in the aqueous phase?

Or I can add span in oil phase as well

Usually you would add the surfactants to separate phases.. I haven't got experience with that system. Just try a small amount and see what happens. Don't be afraid to try things as it is often a lot quicker than worrying about all the options and you will learn something from trying it.

- Usually in spray drying emulsions, I add the surfactant before the maltodextrin.

- For the surfactants, I agree with Vincent: it is easy to do a few small experiments, which will give you reliable data. Much better than relying on advice from unknown people on the internet :-).

- Your idea of putting the Tween in the oil & the Span in the water might be really effective: the emulsifier transport through the interface so that they reach their "happy home" can help make small droplets.

Actually, based on Bancroft rule emulsifier is more soluble in the continuous phase which is water in your system.

I worked with surfactant mixtures and I added the surfactant mix to water. Consider that the total HLB of your surfactant mixture should be higher than 12

However, as Alan and Vincent mentioned surfactants diffuse and will find their proper configuration at the interface. This may take a while for the final equilibration (pseudo-equilibrium might be a better term).

might be a good idea to prepare a coarse emulsion, leave for some time before spray drying so the surfactant mixture reach their optimum configuration at the interface and you can get the best results.

HLB higher than 12???

Optimal HLB will depend on a lot of things, e.g. oil and other components. Given that you have a more complex system indeed testing will lead to faster results than a priory arguing.

Hmm whats the reason to aim for HLB value above 12?

By the way is there such thing as a HLB value range to aim for to produce a

O/W emulsion

or

W/O emulsion?

Roughly how long such I leave the emulsion be how would I know that it has reach final equilibration?As it might just be a weak emulsion after all.

An emulsion is kinetically stable, it never reaches equilibrium. Even if you prevent coalescence their will be Ostwald ripening. I don't think the surfactant equilibrium is anything you should be concerned about

Titus, I do agree that the HLB depends on lots of things. I mentioned the HLB as I have worked with many student who made an emulsion with surfactant mixtures and did not consider the affinity of the surfactant mixture, ended up with reverse or double emulsion. Therefore, as a precaution I just mentioned that it is better to consider the HLB.

Olivia, to my experience, HLB does affect your final emulsion.

Vincent and Titus are far more experienced than me and if they think it is fine with your system then that should be fine.

Elijah, I think the HLB is a useful concept, but one I don't use a lot so I just didn't comment on it. I am more comfortable with the 'critical packing parameter'; these are of course related.

Olivia,

As a general idea if you want to have a water in oil emulsion you want a surfactant that is more hydrophobic and has bulkier hydrocarbon chains (HLB 12-17). if you want to have a water in oil emulsion you want a surfactant that is relatively more hydrophilic and has a larger head-group (HLB ~ 6-11).

If you want to read about the critical packing parameter the original reference is

Theory of self-assembly of lipid bilayers and vesicles

Biochimica et Biophysica Acta

Israelachvili, J. N.

Mitchell, D. J.

Ninham, B. W.

Vol 470

p 185-201

but you will also find it discussed in modern textbooks. I think the cpp idea is more useful for ionic surfactants as it can be used to understand how the properties of the surfactant change with electrolyte concentration or pH.

However all this is a just a guide, you really need to get into the lab and see what happens

Thanks guys for the input!

Will try out in the lab