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PH level

 
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PostPosted: Fri Jun 17, 2005 4:44 pm    Post subject: PH level Reply with quote

What is a good PH for a cream? If a mixture is too acidic, is there any way to increase the PH?
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drtodorov
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Joined: 10 Dec 2004
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PostPosted: Fri Jun 17, 2005 9:46 pm    Post subject: Reply with quote

For a normal non-exfoliating cream, it is reasonable to match the pH of skin mantle, which is between 4 and 5.5
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bobzchemist



Joined: 20 Jun 2005
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Location: Smyrna, TN

PostPosted: Mon Jun 20, 2005 1:51 pm    Post subject: Re: PH level Reply with quote

Anonymous wrote:
What is a good PH for a cream? If a mixture is too acidic, is there any way to increase the PH?


Baking Soda or Milk of Magnesia will adjust pH. Baking soda, NaHCO3, fizzes when added to an acidic solution. The reaction is
HCO3-(aq) + H+(aq) = H2O(water) + CO2(gas)

Milk of Magnesia, magnesium hydroxide, Mg(OH) 2 . The viscous, white, mildly alkaline mixture that is used medicinally as an antacid and laxative is a suspension of approximately 8% magnesium hydroxide in water.


This will increase the salt level in your product, however, which may collapse some emulsions.

The better approach might be to use less acidic material in your formula.

Bob
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orangehrzn



Joined: 23 Feb 2005
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PostPosted: Wed Jun 22, 2005 12:10 pm    Post subject: Reply with quote

In the glycolic acid gels/creams, sometimes they 'buffer' the acid - I guess that means they adjust the PH.

Now if they 'buffer' to skin PH of 5, does that mean that most of the glycolic acid is neutralized to a salt, hence completely useless? How can one adjust the PH wihout neutralizing the acid and hence compormising the very purpose of such products???
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drtodorov
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PostPosted: Wed Jun 22, 2005 11:17 pm    Post subject: Reply with quote

If the purpose of the cream is exfoliation, then you wouldn't want to buffer to pH as high as 5.

Incidentally, there is some evidence that some AHA may have certain benefits beyond pH, particularly lactate. In that case, even at relatively high pH, some effect may remain.
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orangehrzn



Joined: 23 Feb 2005
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PostPosted: Thu Jun 23, 2005 7:38 pm    Post subject: Reply with quote

I still don't understand:

Assume someone has 10% glycolic acid gel. If he buffers it, does that mean the percentage of glycolic acid decreases i.e. part of it turns into a salt. If that is the case, then why not put in directly the final amount of glycolic acid avoiding the need of buffering?

I guess what I don't understand it what exactly the 'buffering' agent is doing. Does it react with the acid turning it into a salt or something else happens?
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drtodorov
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PostPosted: Thu Jun 23, 2005 8:32 pm    Post subject: Reply with quote

You assume that pH is the only thing responsible for the benefits of AHA. If it were true, then any acid, e.g. vinegar, will have the same effect as AHA at equivalent pH. However, it does seem that at equivalent pH AHA (at least some of them) are better than other acids. Therefore, one could suggest that the alpha hydroxy anion (glycolate, lactate, etc.) has benefits of its own. If that is true, raising pH will not eliminate all benefits of AHA because rasing pH removes the acidity (protons) but not the anion.

In one study, for example, AHA improved collagen synthesis in vitro, i.e. in tissue culture where you can't use low pH since cultured cells die at pH below 7. Therefore all of AHA was a salt, and yet there was increase in collagen synthesis and cell growth. (see below)

----------------------

Dermatol Surg. 1998 Oct;24(10):1054-8. Related Articles, Links

Increased in vivo collagen synthesis and in vitro cell proliferative effect of glycolic acid.

Kim SJ, Park JH, Kim DH, Won YH, Maibach HI.

Department of Dermatology, Chonnam University Research Institute of Medical Science, Chonnam National University Medical School, Kwangju, Korea.

BACKGROUND: Glycolic acid treatment is believed to reverse the photoaging process by increasing collagen synthesis in the skin. However, this effect has not been clearly defined even though alpha hydroxy acid products are used extensively. OBJECTIVE: This study aimed to define the primary effect of glycolic acid on collagen synthesis that may be achieved by functional activation or proliferation of fibroblasts. METHODS: Glycolic acid treatment was compared in vivo with lactic acid (hairless mice) and in vitro to malic acid (normal human skin fibroblast culture) with controls. To find the functional activation of fibroblasts, Northern blot assay for type I collagen synthesis with histometric analysis (in vivo) was performed. Cell proliferation assay (MTT) with procollagen type I C-peptide (PICP) enzyme immunoassay and radioisotope ([3H]proline) incorporated collagen production from cultured fibroblasts were determined. RESULTS: The in vivo collagen mRNA expression with histometric analysis revealed greater collagen synthesis by glycolic acid compared with lactic acid and control. In vitro cell proliferative effect of glycolic and greater amount of collagen production showed a steady increase in a dose-dependent manner. CONCLUSION: Both in vivo and in vitro, glycolic acid treatment increased the production of collagen and fibroblast proliferation. These effects may be the mechanism by which glycolic acid reverses the process of photoaging.
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orangehrzn



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PostPosted: Fri Jun 24, 2005 1:03 am    Post subject: Reply with quote

Thanks that makes more sense.
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cjdavis



Joined: 24 Jan 2005
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PostPosted: Tue Jul 05, 2005 11:50 pm    Post subject: Reply with quote

drtodorov wrote:
In one study, for example, AHA improved collagen synthesis in vitro, i.e. in tissue culture where you can't use low pH since cultured cells die at pH below 7. Therefore all of AHA was a salt, and yet there was increase in collagen synthesis and cell growth.

Dr. Todorov, have you seen any ex vivo studies using different ph adjusted (i.e buffered and non-buffered) aha creams?
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drtodorov
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PostPosted: Wed Jul 06, 2005 1:08 am    Post subject: Reply with quote

How do you study a cream ex vivo? You can't just add a typical cream base and/or unbuffered AHA to a tissues culture.
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cjdavis



Joined: 24 Jan 2005
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PostPosted: Wed Jul 06, 2005 7:13 pm    Post subject: Reply with quote

drtodorov wrote:
How do you study a cream ex vivo? You can't just add a typical cream base and/or unbuffered AHA to a tissues culture.

Sorry, I meant to say in vivo, damn Latin =) This mistake wouldn't come as any surprise to some of my bio-geek friends because I am notorious for killing cell cultures accidentally. Dr. Todorov, if you ever want to piss someone off really bad, just forget to maintain the nutrient supply to his cell line he is studying for his masters research. Yes I admit it, Iíve committed il-6 cell homicide!
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drtodorov
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PostPosted: Wed Jul 06, 2005 7:29 pm    Post subject: Reply with quote

cjdavis wrote:
drtodorov wrote:
In one study, for example, AHA improved collagen synthesis in vitro, i.e. in tissue culture where you can't use low pH since cultured cells die at pH below 7. Therefore all of AHA was a salt, and yet there was increase in collagen synthesis and cell growth.

Dr. Todorov, have you seen any ex vivo studies using different ph adjusted (i.e buffered and non-buffered) aha creams?


In that case, if you meant in vivo, I have seen studies of ammonium latate (Lac-hydrin) for various kinds of dry-skin and related syndromes. Try searching medline for Lac-Hydrin.
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