Azeco Cosmeceuticals

1.2.

Exo-polysaccharides & cellulose ethers.

The most frequently used exo-polysaccharides (EPS’s) are xanthan gum, carrageenans and alginates. These biopolymers are usually insoluble in lower alcohols such methanol, ethanol, propanol and isopropanol. Gels based on exo-polysaccharides are broken with a lower alcohol of choice; the alcohol shall not be denatured as the denaturant would complicate the product mixture. The amount alcohol needed must be determined on a case-to-case basis. To the mixture of the precipitated EPS an amount ethoxydiglycol double

the weight of the sample is added to the aliquot to dissolve crystalline azelaic acid. From this point onwards the analytical procedure as described in § 1.1 is followed.

This methodology is usually also applicable for cellulose ethers: methylcellulose (MC), hydroxyethylcellulose (HEC), hydroxypropyl methylcellulose (HPMC), but is not applicable for hydroxypropylcellulose (HPC). HPC is a polymer mostly used to gel anhydrous hy- drophilic solvents such as ethanol, low molecular weight polyethylene glycols (n=6,8) or diacetin/triacetin.

2.

Emulsions.

Emulsion systems are less easily handled than gel systems. It is not always easy to break the emulsion: the emulsifiers used for making the emulsions determine what chemicals must be used to break the emulsion.

2.1.

Emulsions based on non-ionic emulsifiers.

These emulsions are stabilised by the formation of a liquid crystalline system (Israelachvili et.al., 1975) and that is frequently translated in the HLB value of the emulsifier(s): the HLB value is usually 9-11 for stable emulsions. The HLB can be greatly increased to vales > 20 using an anionic emulsifier such as sodium lauryl sulfate or an aliphatic amines such as hexylamine. The addition of alcohol (30% w/w) is usually required to improve the kinetics of emulsion breaking (and to deactivate exo-polysaccharides and/or cellulosics), and a saturated NaCl is added to deactivate acrylic acid-based polymers. The relative amount of the emulsion destabilisers must be de- termined on a case-to case basis. Phase separation may be tedious and time consuming, and therefore the test sample is centrifuged using a standard centrifuge @10,000 rpm during eight minutes. The oil/water interface must be sharp. The two phases are separated and the oil phase is dried with anhydrous sodium sulphate.

Both the oil phase and the water phase may contain azelaic acid and must be analysed according to the methodology as described in § 1.1.

2.2.

Emulsions based on anionic/cationic emulsifiers.

2.2.1. Anionic emulsions are best broken by the addition of sodium chloride (salting out). The amount of sodium chloride may be substantial. Emulsion breaking can further be accelerated by the addition of ethanol. Phase separation may be tedious and time consuming, and therefore the test sample is centrifuged using a standard centrifuge @10,000 rpm during eight minutes. The oil/water interface must be sharp. The two phases are separated and the oil phase is dried with anhydrous sodium sulphate. Both the oil phase and the water phase may contain azelaic acid and must be analysed according to the methodology as described in § 1.1. 2.2.2. Cationic emulsions usually have an acidic pH. These emulsions are best broken by adjustment of the pH to alkaline values (pH>10). The processing should be done quickly as other ingredients may be subjected to hydrolysis. Also here the oil/water interfa- ce must be sharp. The two phases are separated and the oil phase is dried with anhydrous sodium sulphate. Both the oil phase and the water phase may contain azelaic acid and must be analysed according to the methodology as described in § 1.1

Mussenberg 1 • 6049 GZ Roermond • The Netherlands

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