Greifensee, Switzerland. July 20, 2011. Skin moisturizing products are developed and manufactured to target different areas of the body. They consist of two basic formulas: oil in water and water in oil. Analyzing the moisture content of skin moisturizing creams is a key aspect in end product quality control. It also helps to ensure that the end product is suitable for its intended and marketed use.
The Instrument of Choice
Oil in water formulas are light liquids or lotions that do not feel heavy on the skin. The majority of the formula is water which may evaporate on the skin and leave a small amount of oil. Water in oil formulas are heavy, greasy products consisting mostly of oil. Generally, water in oil products are developed for skin that has a good water content but requires more oil from a moisturizing product.
Thermogravimetric analysis (TGA) is an excellent tool for analyzing the moisture content of cosmetic skin creams. The results shown in the figure (right) were measured using the METTLER TOLEDO TGA/DSC 1 and evaluated using STARe Excellence software.
Samples of oil in water (o/w) creams with different water contents were heated from 20 °C to 200 °C at a heating rate of 2 K/min in a nitrogen atmosphere. The TGA curves indicate that all creams, with the exception of sample C, show a significant weight loss between 30 °C and 140 °C. The weight loss is caused by the evaporation of volatile components, especially water.
The TGA/DSC 1 is a valuable instrument for product quality control within the cosmetics industry. It provides excellent and reliable thermogravimetric measurement performance and high temperature accuracy. With the addition of the sample robot, hermetically sealed crucibles can be pierced immediately prior to measuring.
This unique feature prevents the sample taking up or losing moisture between weigh-in and measurement. The TGA/ DSC 1 also has the added benefit of simultaneous calorimetric analysis, which is of great benefit to cosmetics manufacturers.
