QUANTITATION OF TITANIUM DIOXIDE 381 Powder Make-Up Base 30 30 y = 0.9633x + 02491 y = 1.0332x - 0.08 25 R2 = 0.9993 25 R2 = 0.9997 I. ,♦ � 20 * 20 lJ lJ � Q) ::, :5 15 U) 15 U) CCI CCI Q) Q) � � C\J 10 t' C\J 10 • 0 0 i= i= 5 • 5 .. 0 • 0 0 10 20 30 0 10 20 30 TiO2 Added (%) TiO2 Added (%) Cream Foundation 30 30 y = 1.0443x - 03137 y = 0.9578x + 0.1897 25 R2 = 0.9991 J 25 R2 = 0.9996 I * 20 � 20 lJ lJ � Q) ::, :5 U) 15 U) 15 CCI CCI Q) Q) � � N 10 ,I: N 10 I[ 0 0 i= i= 5 • 5 � • 0 0 0 10 20 30 0 10 20 30 TiO2 Added (%) TiO2 Added (%) Fi g ure 2. R 2 values of the tit rations in diverse cosmetic formulations. titanic acid," such as [Ti(OHMH2O2)(H 2 O 2 )h + or (TiO 2 .aq) 2 +, with hydrogen perox­ ide (8). Since Beer's Law is obeyed up to 50 ppm of titanium, this method is good for analyzing trace levels of titanium (9). However, chromium that originates from cosmetic colorants such as chromium oxide green or chromium hydroxide green interferes with the analysis by forming colored material with hydrogen peroxide. Ferric ions that

382 JOURNAL OF COSMETIC SCIENCE Table I Recovery Tests for the Titanium Dioxide in Four Types of Cosmetic Formulations Recovery (%) in each cosmetic formulation Added amounts ( % ) Cream Make-up base Foundation Powder 1 98.0 ± 3.0 103.0 ± 5.0 96.0 ± 9.0 97.0 ± 4.0 5 99.2 ± 4.6 96.6 ± 9.0 104.8 ± 6.0 101.6 ± 4.2 10 96.6 ± 5.5 104.7 ± 6.5 97.2±4.2 102.5 ± 7.4 25 103.8 ± 3.0 102.8 ± 4.4 96.4 ± 3.6 96.8 ± 3.9 Table II Comparison of the Results from Volumetric Titration and ICP-AES Measured Ti02 (%) No. Cosmetic Type Titration ICP-AESa Cream 2.9 ± 0.12 2.8 ± 0.10 2 Lotion 5.4 ± 0.21 5.1 ± 0.15 3 Cream 4.7 ± 0.19 4.9 ± 0.14 4 Make-up base 1 4.8 ± 0.17 4.7 ± 0.16 5 Make-up base 2 4.8 ± 0.14 4.5 ± 0.15 6 Foundation 10.6 ± 0.26 10.8 ± 0.32 7 Powder 12.4 ± 0.34 12.9 ± 0.40 "ICP-AES was performed by Anapex Research Inc. (Yusung, Korea) ongrnate from cosmetic colorants, iron oxides, also interfere by producing yellow­ orange-colored solutions in acidic media. Since there are many metal oxide pigments, including chromium oxides or iron oxides, it is difficult to use the colorimetric method to determine the level of titanium in the cosmetics. Gravimetric determination is a traditional analytical technique for titanium measure­ ment. This involves the production of a yellow flocculent precipitate, Ti(C6H502N2)4, of cupferron and titanium in acidic solution (10). Since other metals can be co­ precipitated in this procedure, it is necessary to use a selective precipitating agent. This method is not so good for everyday routine work, since it requires some manipulative analytical skills and is somewhat time-consuming. Nowadays, analytical instruments have become powerful research tools for analytical research. There are many techniques, including flame or electrothermal atomic absorp­ tion spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Because of the poor activation efficacy of titanium in the flame, it is difficult to exploit flame AAS. Electrothermal AAS is also not widely employed, since many other elements make stable titanium complex in the furnace. Since ICP has sufficient energy for the atomization of titanium, ICP-MS and ICP-AES can effectively determine the titanium. They are the best methods for trace level measurements. Their detection limits are in the range of 1 to 10 ppt for ICP-MS (7). Although instrumental techniques, such as ICP-MS or ICP-AES, are the best for the analysis of titanium, only a minority of cosmetic companies would be able to afford them because of their high cost.