Hi Emil!

This is more of a general note on surfactant work. I have no experience in this mixture, but hopefully there is something useful for you below:)

One things you should consider is the starting concentration. If you do dilution from concentrated stock solutio to very dilute, say ppm, the process takes quite long. Mixing is necessary, but you may have problems with foaming. Also check your pipettes and evaluate the pipetting error. Viscous fluids are sometimes challenging to work with.

Usually, dilutions from stocks are left to stabilise over night at least. But as always, depending on the chemical. A dilution from pure to dilute should be done in steps. Make a mother solution that is between your target and the stock and leave it to stabilise. The solution should ideally be clear and the colour even. Then make the final dilution. If you have a system (bubble pressure or optical tensiometer) that allows you t take measurement over longish time, do that. I recommend you use the entire solution as sampling a fresh mixed solution may have higher errors. If you do so, sample while mixing.

Since you work with surfactants, take also care that you use materials on which your molecules do no willingly adhere. The longer the storage time, more losses or chemical reactions like oxidation you introduce. Therefore, I advise you to do some trials and then use always solutions of the same age.

Hope that helps more than confuses!

Make repeated measurements over a period of a day and see how long it takes the readings to stabilize. It's the only way you can be sure how long to wait.

Hi Laura and John,

Thank you for your useful answers.

Regards,

Emil