Quality Control of Lipstick and Mascara by Thermal Analysis

Many different sorts of lipstick and mascara are nowadays available. The most important characteristics of these products are that the effect lasts a long time, that the products are easy to apply and easy to remove, and that they are physically and chemically stable and do not irritate the skin. The waxes and oils in lipstick are responsible for ease of application; carbon black is often used as pigment in mascara. Thermal analysis techniques allow the quality of these types of cosmetic products to be easily checked.

Introduction

There is an ever increasing demand for lipsticks, mascara, hair colors and creams on the cosmetic market. Cosmetic products often have complex formulations, which is the reason why good analysis techniques are needed to monitor the quality of such products.

The following application examples show how DSC and TGA were used to analyze different types of lipstick and mascara..

Lipstick is a cosmetic product that consists of oils (50–65%), waxes (10–20%), fats or plasticizers (10–20%), pigments (10–15%) and additives such as antioxidants. Its primary function is to provide color and protection for the lips. Many types of lipsticks are nowadays available. The main features of a lipstick are that its effect last a long time, that it provides a glossy or a matt effect, that it is easy to apply and easy to remove, that it is physically and chemically stable, and that it does not irritate the skin.

The waxes employed are usually beeswax (melting point about 65 °C) or carnauba wax (melting point about 85 °C). The latter is responsible for the stability of the lipstick because of it high melting point so that the lipstick first softens in contact with the lips. In addition, the wax provides gloss. In contrast, beeswax creates a matt effect.

The oils used are castor oil, olive oil, coconut oil or jojoba oil. Oils facilitate the dispersion and stabilization of the pigments and also promote a beneficial skin care effect. Fats such as shea butter or lanolin are used as plasticizers. Lanolin in addition provides a certain adhesive effect. Diverse organic and inorganic pigments are used for coloring.

The inorganic pigment titanium dioxide offers additional protection against UV radiation and has high covering power [1].

Waxes and oils are the main constituents of lipsticks. They can be easily characterized by DSC through their melting behavior [2]. This enables different lipsticks to be quickly and easily compared and differentiated.

Mascara is a type of eye make-up used to darken, thicken, and lengthen eyelashes. Mascara exists in different formulations, for example liquid or cream like. Besides oils and waxes, pigments are also important constituents that are used to provide color. The FDA (United States Food and Drug Administration) issues rules and regulations (CFR - Code of Federal Regulations) about the ingredients allowed in different cosmetics like mascara.

For example, only natural colors or inorganic pigments such as carbon black, iron oxide or ultramarine blue can be used near the eye. The pigments allow products to be colored black, brown or blue. Furthermore, the content of carbon black in mascara must not exceed 10% [3]. This value must be routinely controlled and is very easy to check by TGA.

Conclusions

DSC and TGA play an important role in the quality control of cosmetics. DSC can be used to characterize the melting behavior of waxes and oils in lipsticks. For example, we expect a lipstick that melts at low temperature to spread easily over lips whereas a lipstick with a higher melting point can be worn for a long time.

TGA is the preferred technique for obtaining information about the content of carbon black in mascara. It is important to monitor this value because the carbon black contents in mascara formulations must be less than 10%.

_{Quality Control of Lipstick and Mascara by Thermal Analysis | Thermal Analysis Application No. UC 445 | Application published in METTLER TOLEDO Thermal Analysis UserCom 44}