Vol.42, No.1, pp.36‐39, 2008
Determination of diethylene glycol in toothpaste

Abstract

When fluid is mixed by a rotor and small vessel that has a narrow clearance between its wall and the rotor with the upper part covered by an endplate, the processing fluid becomes a high-speed thin-film spin flow. This flow possibly allows the peripheral speed to be over 30 m/s, which was unable to be obtained by a conventional high-speed mixer. As a result, the processing fluid obtains more and homogenous energy. In an actual experiment, we compared a high-speed thin-film spin mixer with a conventional high-speed mixer upon an emulsification experiment with soybean oil. The experiment proved that the former mixer could control the particle size distribution. It also proved that the same result could be obtained by continuous operation as by batch operation. In conclusion, the high-speed thin-film spin mixer can control particle size distribution with a high efficiency.A rapid and simple method using gas chromatography (GC) for the determination of diethylene glycol (DEG) in toothpaste was developed. DEG in toothpaste was extracted with methanol containing 1,4-butanediol as the internal standard by using an ultrasonic bath. The centrifuged and filtrated methanol extracts were analyzed by GC on an InertCap 624 capillary column. The recoveries of DEG from toothpaste fortified at the levels of 0.1, 0.5 and 1.0%, were 103.6, 99.9, 99.4%, respectively. The quantitation limit of DEG in toothpaste was 0.05??%. The proposed method could be applied to other cosmetics on the market without any interference. By using this method, DEG was detected the presence in two out of 10 toothpaste samples set to the hotel. This analytical method should be useful for quality control for manufacturers and importers of cosmetics.