Hyaluronic acid gel with small silicone phase separating
We are developing a serum with 2% sodium hyaluronate and a small silicone phase in suspension, but in stability we are seeing the gel separate after about 2 weeks at 45oC and about 4-6 weeks at 25oC, leaving a clear water layer on the bottom that slowly increases, and an upper milky layer. We are also developing a vitamin serum at the same time with the same base formula which is not displaying this behavior, so I am thinking it has to do with the hyaluronic acid - not sure if maybe there are too many water absorbing ingredients in competition for the water? Below is the formula, pH about 5 and forms a very thin gel.
QS water (about 73%)
0.03% citric acid
0.5% probiotic in maltodextrin
0.2% sodium gluconate
3% spectrastat PHL (Caprylhydroxamic Acid,1,2-Hexanediol, Propanediol)
0.15% xanthan gum
0.1% sodium hyaluronate >1.8 MDa
0.1% sodium hyaluronate 1 - 1.8 MDa
0.2% sodium hyaluronate 0.2 - 0.6 MDa
1.6% sodium hyaluronate <20 kDa
6% dimethicone 100 cS
2% liquid shea butter
1.6% Simulgel NS (Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Squalane, Polysorbate 60)
Any ideas what might be causing the separation and how to counter it? We have tried replacing the xanthan with Sepimax Zen, but same result (and started separating about a week earlier). We don’t want to increase the viscosity because of the packaging. Thanks in advance for any advice!