How to know if it is SLS or SLES liquid?

Here a supplier is selling SLS liquid but i doubt if it is SLS or SLES. Is there any to identify if it is SLS or SLES? 

Comments

  • PerryPerry Administrator, Professional Chemist
    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_TogeBill_Toge Member, Professional Chemist
    edited October 2021
    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
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • PerryPerry Administrator, Professional Chemist
    edited October 2021
    @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!

  • @Perry @Bill_Toge thanks 

    I will do 5his cold test. It is easy
  • Bill_TogeBill_Toge Member, Professional Chemist
    edited October 2021
    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
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • PharmaPharma Member, Pharmacist
    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?
  • @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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