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Sodium hyaluronate - pH increase
Hi,
Some company was to prepare a sample of the product with sodium hyaluronate for me. I noticed that instead of a pH 5, the product had a pH 6. The ingredients were tested separately and it was found that sodium hyaluronate caused the increase. The problem was not resolved and I gave up on it, but I wonder what could be causing this increase? I guess the possible cause was that the sodium hyaluronate may not have been fully dissolved while making the sample. A slight increase in pH was observed a few hours after making the sample, and it increased over the following days. Any ideas? It was high molecular weight sodium hyaluronate at 0,40%.
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11 Replies
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All they need to do is make a pH adjustment after fully hydrating the sodium hyaluronate. Is the issue that they are seeing a rise in pH even after making the pH adjustment or are they not making the pH adjustment at all?
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@MarkBroussard They did pH adjustment with citric acid after mixing sodium hyaluronate. They said it was impossible that sodium hyaluronate did not fully dissolve because it would be visible and the idea to solve it was to first add citric acid to the water (in such an amount that finally the product had a pH of 5), and then add sodium hyaluronate. Just change the order. Does it make sense?
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No really … but let them try changing the mixing order of Citric Acid and see if that makes a difference.
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@MarkBroussard How do you know if sodium hyaluronate is fully hydrated?
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When your solution becomes uniform. If it is not fully hydrated you will see balls of HA circulating around.
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I was just trying to dissolve it. The “balls of HA” did show up, but they dissolved very slowly. I wonder if maybe this pH increase was due to the HA being 90% dissolved, so that it wasn’t readily noticeable that it wasn’t completely hydrated. But I don’t know if this would be able to increase the pH by 1. On the other hand, the problem arose when the HA was changed to one with a higher molecular weight.
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The higher the MW of the HA the longer it generally will take to fully hydrate. You just have to keep it stirring until it is fully hydrated and that can take a couple of hours or so.
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I always pre-make my HA, and store the slurry in the refridgerator. Hence, never waiting, never wondering.
When you do this…you have to add a preservative to the mix at this point.
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Thanks @MarkBroussard @Graillotion
@Graillotion Yes, I’ve always done it this way too, but for larger amount, I guess it could be problematic…I made three samples. In the first sample, I still don’t know what exactly I did wrong, after I couldn’t see the “balls” anymore, I kept mixing for 5 minutes (probably too short). After half an hour, the pH increased by 0.1. I checked later in the morning and there was a total increase in pH of 0.7
Then I did two more samples, after that the solution looked uniform, I continued to mix for 20-30 minutes and there is no increase after 24 hours. So I guess it worked 
But I have a second problem. If I add Euxyl pe 9010 after dissolving the hyaluronic acid, the solution is cloudy, whitish. It is not very visible, but it is definitely not transparent, and it should be. I managed to get a transparent solution by mixing Euxyl with propanediol, then I added water, and finally hyaluronic acid. But if I do it in reverse order and add euxyl at the end it remains cloudy even after long stirring. I even tried to heat the solution but it doesn’t help at all. Why is this happening?
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grapefruit22 said:Thanks @MarkBroussard @Graillotion
@Graillotion Yes, I’ve always done it this way too, but for larger amount, I guess it could be problematic…I made three samples. In the first sample, I still don’t know what exactly I did wrong, after I couldn’t see the “balls” anymore, I kept mixing for 5 minutes (probably too short). After half an hour, the pH increased by 0.1. I checked later in the morning and there was a total increase in pH of 0.7
Then I did two more samples, after that the solution looked uniform, I continued to mix for 20-30 minutes and there is no increase after 24 hours. So I guess it worked But I have a second problem. If I add Euxyl pe 9010 after dissolving the hyaluronic acid, the solution is cloudy, whitish. It is not very visible, but it is definitely not transparent, and it should be. I managed to get a transparent solution by mixing Euxyl with propanediol, then I added water, and finally hyaluronic acid. But if I do it in reverse order and add euxyl at the end it remains cloudy even after long stirring. I even tried to heat the solution but it doesn’t help at all. Why is this happening?
I used to formulate with Optiphen, so when I switched, I had some leftover. This became my preservative to use up for the HA solution. It is crystal clear….or at least it is…the next day. Which is the only time I evaluate it.
Aloha and good luck.
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Hi there right or wrong the way I make my HA solution (based on 100 g) is weight 98 g Distilled Water + add 1g Plantaserve (mine is Phenoxyethanol 90%, Ethylhexylglycerin 10%). Mix this until combined. Then I weight (spinkle) 1 g HA Powder and then I let it hydrate by itself for a few hours (cover beaker in clingfilm). After a few hours I then mix with a mini-blender and then leave sit again for a few hours - by then mine is a clear thickish gel/liquid. I bottle it and keep in fridge.
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