Azeco Cosmeceuticals

Dosage of finished forms

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 satu rated NaCl is added to deactivate acrylic acid-based polymers. The relative amount of the emulsion destabilisers must be determined 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. 2.2.1. 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 con suming, 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 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. Polymeric emulsifiers behave in a similar fashion as acrylic acid-based polymers (see § 1.1) and these emulsions are easily broken using a saturated NaCl solution. 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. There is no general procedure available for the quantitative determination of the assay of Azelaic acid in consumer products; a general procedure is also not possible.. Good laboratory practice and creativity of the analytical chemist(s) are prerequisites for the performance of the quantification of Azelaic acid in consumer products. 2.2. Emulsions based on anionic/cationic emulsifiers. 2.3. Emulsions based on polymeric emulsifiers.

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