140 JOURNAL OF COSMETIC SCIENCE Table II Irradiation Conditions under Natural Sunlight (12:00 h-15:30 h solar time, in May-June, Toulouse, 43° North, France) for Preparations Containing 1 % w/w of Absorbers Total concentrations UV intensity* Irradiation Absorbers (mmol 1- 1 ) (mW cm-2) experiments BM-DBM 27 3.6-4.7 P'l ClO-DBM 19 3.6-4.7 C'l and C'2 BM-DBM/ClO-DBM (7:3) 19 3.4-4.4 M'l Preparation specific gravity = 0.934 g cm- 3 and irradiated area = 16 cm2. * Radiometer: Oriel Instruments. Film Sample weight thickness (mg cm- 2 ) (µm) 0.9 10 0.8 9 0.9 10 The solvatochromic properties of the molecule were first investigated in organic solvents. In acetonitrile, the molecule absorbed in the UVB-UVC domain (Figure 3), with a maximum absorption at 263 nm. UV spectra of the diketo ClO-DBM were recorded in dichloromethane, hexane, ether, pentanol, isopropanol, and methanol. We noted that the wavelength of maximum absorbance ("-max did not fluctuate much (between 262 nm in hexane and 268 nm in dichloromethane), and the molar absorption coefficient at "-max ranged from 20 000 M- 1 cm - 1 in acetonitrile to 2 5 000 M- 1 cm - l in hexane. When Cl0-DBM was incorporated in an organized environment, a micellar solution of SDS (5 x 10- 2 mol 1- 1 ), the UV spectrum (Figure 4) showed two absorption bands: a first band corresponding to the diketone form, with a maximum absorbance at 271 nm, and a second corresponding to the enol form at 361 nm. An organized environment seemed to favor the enol form, which absorbed UVA rays. BEHAVIOR UNDER IRRADIATION WITH A 150-W XENON LAMP In organic solvents. Figure 5 shows the absorption spectrum recorded before (dotted curve) 1 0,9 0,8 0,7 0,6 Q) 0,5 0,4 0,3 0,2 0,1 0 200 250 300 Wavelength (nm) 350 Figure 3. UV spectrum of ClO-DBM in acetonitrile (2.9 x 10- 5 M). 400

0,9 0,8 0,7 0,6 C m .0 0,5 .0 0,4 : 0,3 0,2 0,1 0 200 Figure 4. 1 0,9 0,8 0,7 � 0,6 C m 0,5 0,4 0,3 . \ 0,2 0, 1 0 200 NEW LONG-CHAIN UV ABSORBER 361 nm 271nm 250 300 350 Wavelength (nm) UV spectrum of Cl0-DBM in an aqueous micellar solution of SDS (5 x 10- 2 M). # 250 300 Wavelength (nm) # # # 359 nm ----. .... . 350 141 400 .. 400 Figure 5. UV spectra of BM-DBM in acetonitrile (2.2 x 10- 5 M) before irradiation (dotted line) and after five minutes of irradiation (full line) with a 150-W xenon lamp (P = 20 mW cm- 2 ). and after (full curve) five minutes of irradiation of BM-DBM in acetonitrile. When a solution of BM-DBM in acetonitrile was irradiated for five minutes (xenon lamp, P = 20 mW cm- 2 ), a strong fall in the UVA absorbance at 359 nm was observed, while the UVB absorbance increased, with a maximum at 267 nm. Figure 6 shows the absorption spectrum recorded before (dotted curve) and after (full curve) five minutes of irradiation of Cl0-DBM in acetonitrile. Irradiation of a solution