preservative mix phenoxyethanol And sodium benzoate and potassiom sorbate

Hello experts
I am new to cosmetic formulating and giving a try to lotion making. But I have limited access to preservatives where I live. (as I can't place order in bulk). 

So basically I have phenoxyethanol, DMDMH,  sodium benzoate, Potassium sorbate available here. I wish to keep pH of my product at 5-6.

I read a lot about preservatives online; And concluded that I can use phenoxyethanol + sodium benzoate + Potassium sorbate blend as a preservative as it will cover bacteria, mold, yeast. It's just my idea and there is no literature to support it. So I am seeking some guidance. 

Will it be a good combination though?
I am not sure about what proportions to keep of these 3. 
Also do I need to dilute Sodium benzoate and potassium sorbate before mixing in phenoxyethanol? 
What will be solubility of this blend, how much % should be used in final product to get broad spectrum coverage?

It will be of great help if you can clear these doubts. Its giving me a brain wreck.
Thank you in advance.

Comments

  • If you want to formulate at pH 5-6 then Sodium Benzoate and Potassium Sorbate won't be very useful. They are most effective at pH levels below 5.

  • Thank you for replying. I read somewhere that sodium benzoate activates below 5.5 pH, its activity being 60% at that pH level. I agree that it is at its best (94% effective) at lower pH like 3. But I hope it will work at pH 5. Also skin's pH is 5.5, I guess.
  • In the area of preservation, hope is not a good guide. In truth, I'm of the opinion that people should stick with things that have been demonstrated to work time and time again (parabens and formaldehyde donors). When you go with a food preservative like sodium benzoate it brings along with it formulation challenges and questionable safety.

    But you can try whatever you like. Using a 60% active preservative doesn't seem like a good idea to me.
  • K-Sorbate is effective at the Pka of sorbic acid ie 4.76 but the latter discolors in storage .
  • I would prefer to use the time tested preservatives but I don't have access to parabens, at least not in small quantity. 

    I can use DMDMH if you advice so. Will it cover all the microorganisms? 
    Or what should it be combined with to achieve broad spectrum activity?

    I am looking for preservation of lotions/creams and IF it allows masks.
  • DMDMH is broad spectrum and good for categories you listed:use level 0.5%.
  • @DRBOB@VERDIENT.BIZ  thank you for the suggestion, I will try it.
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