Home Cosmetic Science Talk Formulating General How to know if it is SLS or SLES liquid?

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  • OldPerry

    Member
    October 6, 2021 at 1:29 pm

    Ideally, you would take a sample and run it through an IR Spectrophotometer. Then you could just compare it to a standard.  That is what big/medium sized companies do. You should also have a Certificate of Analysis which lists specification ranges. You could also check for 1,4 Dioxane levels.   SLS should have none while SLES might have some detectable levels.

  • Bill_Toge

    Member
    October 6, 2021 at 7:20 pm
    if it’s around 26-28% w/w, chill some of it to 0-5°C - SLS will solidify before it gets that cold, while SLES will remain liquid
    @Perry IR wouldn’t be much use in this case - the C-O stretches in aliphatic  ethers occur at low wavenumbers (1100/cm or less), making them hard to distinguish from the “white noise” often found in that region
  • OldPerry

    Member
    October 6, 2021 at 8:26 pm

    @Bill_Toge - thanks! Admittedly, this is the kind of question we farmed out to our QA/QC department. It seemed they routinely ran IR on everything. Your solution is much more elegant!

  • Abdullah

    Member
    October 7, 2021 at 2:49 am

    @Perry @Bill_Toge thanks 

    I will do 5his cold test. It is easy

  • Bill_Toge

    Member
    October 7, 2021 at 7:18 pm

    Perry said:

    @Bill_Toge - thanks! Admittedly, this is the kind of question we farmed out to our QA/QC department. It seemed they routinely ran IR on everything. Your solution is much more elegant!

    no worries!

    infamously I once had a colleague who insisted on taking an IR spectrum of sodium fluoride, which is completely invisible in IR, so the spectrum showed nothing but the air
    I can only conclude she either slept through the organic/inorganic labs at university or forgot about them completely once she’d left
  • Pharma

    Member
    October 7, 2021 at 7:55 pm
    I don’t know about SLES but identity determination according to pharmacopeias of longer PEG chains than the 2 in SLES is actually determined using FT-IR.
    You could check out pharmacopeia guidelines for SLS and SLES… some are identical because they determine the sampe part of the molecule. Maybe a colour reaction in solvents could be feasible?
  • Abdullah

    Member
    October 8, 2021 at 1:17 am

    @Pharma @Bill_Toge thanks. 
    I did place it and an SLES 25% liquid in freezer. After sometime this one solidified but SLES 25% was liquid. So i can be sure it is SLS not SLES as Bill said. 

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