Precipitate in skin cleanser

Dear members,

The following formulation is tried in the lab.

1. Chlorhexidine Gluconate 20% Solution - 20% (4% active)
2. Ethanol Anhydrous - 4%
3. Lauramine Oxide (Ammonyx LO) - 4%
4. Alkyl Polyglucoside (Caprylyl Glucoside) - 2%
5. Glycerol - 0.02%
6. Hydroxyethyl Cellulose (100,000 grade) - 0.26%
7. Fragrance - 0.1%
8. Colorant (Carmoisine E122) - q.s

After a few days, there are tiny precipitates at the bottom of the container. What could be the reason behind those tiny precipitates ? 

Is APG compatible with HEC or Cellulose in general ?

Comments

  • @MurtazaHakim What's the pH of your formula? I don't have much experience with CHG, but I found some information where it says that CHG could precipitate at a pH outside the range 5.5-7.0 (https://www.supleasepticos.com/wp-content/uploads/chg-compatibility-.pdf).
  • MurtazaHakimMurtazaHakim Member
    edited February 16
    The pH of the formulation exceeds 7. It was measured as 7.6. Which pH adjustment agents are suitable for pH adjustment of CHG based products ?

    Citric Acid is considered to inhibit the activity of CHG that is why it does not seem to be suitable for the pH adjustment. 
  • PerryPerry Administrator, Professional Chemist
    edited February 16
    A solution of HCl could probably be used to adjust the pH.
    What is the purpose of using the CHG in a skin cleanser?
  • It is a medical product. A 4% w/v CHG skin cleanser to be used for pre-operative handwash and surgical skin cleanser.

    HCl is a strong acid and may not be suitable for such a product. 
  • PerryPerry Administrator, Professional Chemist
    You don’t need a high concentration of HCl to adjust the pH. But phosphoric acid or acetic acid could work too
  • The document shared by Ketchito indicates that a variety of commonly used acids and bases result in inhibiting the activity of CHG. 

    Which option remains then to adjust the pH ?
  • Bill_TogeBill_Toge Member, Professional Chemist
    chlorhexidine is a notoriously cranky material to work with, having a +4 charge on the cation - it's most likely the alcohol that's causing you grief
    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
  • I have tried formulating my product considering Hydrex Surgical Scrub which is a known product from Ecolab. It has Ethanol too. What could be the reaction between Ethanol and CHG ???

    I think the precipitate is chlorhexidine base due to the fact that the pH of my product is slightly alkaline (7.6).

    I think gluconic acid or lactic acid should be used to adjust pH to 6. If the precipitate appears even after obtaining pH 6, then the reason for this precipitation may be different.
  • Bill_TogeBill_Toge Member, Professional Chemist
    it's not reacting with alcohol, alcohol reduces its solubility in water
    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
  • Is there a specific sequence of addition I should follow ???

    I dissolve HEC in Water in one phase and then add the surfactants diluted in water and then add the fragrance which is dissolved in Ethanol and then water to q.s to 100 vol%.

    APG has high pH. That maybe the reason for alkalinity of the finished product. 
  • PhilGeisPhilGeis Member, Professional formulator
    CHG is a poor preservative.
  • Its a formulation which is specifically for pre-operative and post-operative hand wash. CHG in this formulation is not intended as a preservative but is an active ingredient for skin antisepsis.
  • PhilGeisPhilGeis Member, Professional formulator
    what is the preservative?
  • 4% w/v of CHG is the active ingredient. A formulation with such a high % of CHG should not require any other preservative.
  • PhilGeisPhilGeis Member, Professional formulator
    edited February 22
    4% w/v of CHG is the active ingredient. A formulation with such a high % of CHG should not require any other preservative.
    Wrong.  Or perhaps you can prove it.

    To note in  your "proof" - https://www.cambridge.org/core/journals/infection-control-and-hospital-epidemiology/article/outbreak-of-burkholderia-cepacia-bacteremia-caused-by-contaminated-chlorhexidine-in-a-hemodialysis-unit/85154B587466D8DD5BFC9F9971CDF95E

    https://academic.oup.com/jimb/article/42/6/905/5995474?login=true

    and many other such reports in google scholar.
  • PerryPerry Administrator, Professional Chemist
    @PhilGeis , @MurtazaHakim - It seems, life finds a way!


  • Try Distilled water?
  • I understand that there may be contamination but the source of contamination is water. My concern currently is the precipitation in the product which is visually impairing the product. The antiseptic efficacy of the product is a different subject overall.

    I am attaching a photograph of Ecolab's product label for Hydrex Surgical Scrub. The label indicates the active ingredient as well as excipients.

    pH adjustment is an issue which I am trying to solve. The document uploaded by Ketchito indicates that lactic acid may inhibit the antimicrobial activity of CHG which discourages me to use it but I have found patents of similar product using lactic acid for pH adjustment. 
  • PhilGeisPhilGeis Member, Professional formulator
    edited February 23
    The quality of their product is not the quality of your product.   Can you share your risk assessment?
  • I respect your opinion Mr. Phil but let us not deviate from the subject which is the precipitate. I posted the above files in order to indicate that CHG 4 % w/v may not require any other preservative. 

    The quality of such products is evaluated primarily and most importantly by efficacy testing against bacteria, virus, fungi, yeast etc. The question currently is concerned with the stability of the formulation itself. The efficacy testing can be executed once the formulation is found to be stable. 
  • ozgirlozgirl Member, PCF student
    The Ecolab product does not contain an alkyl polyglucoside surfactant. The glucoside surfactants often have a high pH (11-12) which could also be raising your overall pH and causing the precipitate.

    Try removing the glucoside and see if that fixes the issue.
  • Bill_TogeBill_Toge Member, Professional Chemist
    ozgirl said:
    The Ecolab product does not contain an alkyl polyglucoside surfactant. The glucoside surfactants often have a high pH (11-12) which could also be raising your overall pH and causing the precipitate.

    Try removing the glucoside and see if that fixes the issue.

    also, the Ecolab product contains an amphoteric surfactant (the amine oxide) which could very well help the chlorhexidine remain in solution by partially shielding the high positive charge
    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
Sign In or Register to comment.