Spectrofluorometric Study of the Inclusion Complexation of Fluorescent Whitening Agents and β-Cyclodextrins

The inclusion complexation behavior of 2,5-Bis(5-tert-butyl-benzoxazol-2yl)-thiophene (UVOB) with native β-cyclodextrin (βCD) and βCD-monochlorotriazinyl (βCD-MCT) was evaluated by fluorescence spectroscopy. The association constant (Ks), stoichiometry, , and were evaluated at 25℃ ± 0.1℃ in phosphate buffer solution (pH = 10.5, 0.1 mo•dm–3) in order to find out the complex formation ability and stability. Fluorescence enhancement for UVOB and UVBNB with both CDs has been observed as a result of the complex formation. A stoichiometry 1:1 for UVOB in both CDs was observed;a stoichiometry 3:1 for UVBNB in both CDs has been observed. The Ksvalues for UVOB were 4916 ± 137 M–1 and 655 ± 19 M–1 (acetone: water 90/10, v/v) with βCD and βCD-MCT, respectively. The value obtained indicates a spontaneous and stable complex formation, but the complex βCD-UVOB showed high Ks value as an indicative of a high concentration of complex formed. Additionally, Ks and thermodynamic parameters and were evaluated in a commercial product UVBNB (UVOB, 13%, v/v). In aqueous solution, the values obtained were 2552 ± 115 and 1787 ± 75 M–1 respectively. Complexation of UVOB with CDs is an interesting approach for utilization of UVOB in aqueous systems without the need of solvents and or surfactants used in commercial product (UVBNB).

Direct Determination of Migration Amount of Fluorescent Whitening Agents in Facial Mask

Facial mask is a kind of skin care cosmetics, in which fluorescent whitening agents（FWAs） were added to make face skin look whiter and brighter. In this work, pig skin was used instead of human skin to test the methods. Three methods, including pig skin migration fluorescent spectrophotometry（FS）, fiber paper migration FS, and fiber paper migration visual colourimetry（VC）, were developed for determining the migration amount of FWAs from facial mask to pig skin. In the methods, a self-assembly light source and fluorescence collecting unit was used. The unit can be easily moved and the measurement was very convenient. Some experimental conditions were optimized. The fiber paper migration VC can give semi-quantitative results and was the simplest one in the three methods because collec- tion, separation and detection of the fluorescence were not needed. Both the pig skin migration FS and fiber paper migration FS can give quantitative results and compared with fiber paper migration FS, the pig skin migration FS could give more practical results by simulating the real way of using facial mask. The limits of detection for disodium 4,4＇-bis[（4-anilino-6-hydroxyethylamion-1,3,5-triazin-2-yl）amion]stilbene-2,2＇-disulphonate（VBL） obtained by pig skin migration FS and fiber paper migration FS were 0.03 and 0.05 mg/m2, respectively. 96 kinds of samples were analyzed and the migration amounts of FWAs in 21 kinds of samples were detectable. Correlations between migration amounts obtained by the three methods were very good. Experimental results indicate that the present methods can be applied to the determination of migration amount of FWAs in facial masks.