Stability Study of Avobenzone with Inorganic Sunscreens

Stability Study of Avobenzone with Inorganic SunscreensUyen Ngu yen and David SchlossmanKobo Products, Inc. - 690 Montrose Avenue - South Plainfield, NJ 07080I ntroductionT itan iu m diox ide and zinc oxide are pr efer able UV A / UV B sunscreens because of their efficiencya nd low ir r itat ion. In or der to i ncr ease th e p r otection in the UV A r ang e, in m a ny count r ies,Avobenzone has been u sed in com bin ation with titanium dioxide and / or zinc oxide. H owever , int h e US A c om b in a t i on s of Av ob en z on e a n d p h y si ca l su n scr een s a r e n ot p er m i t ted.Avoben zon e has been r epor ted to be unstable when con tained in for m ulation s with p hysicalsunscr eens. S urface coating of the p igm en t has som etim es been sh own to incr ease its stabilityObjectiveIn th is study com binations of Avoben zon e and inor gan ic pigm ents wer e ir r adiated in order todeterm in e the influence of the pigm en ts an d th eir surface tr eatm ents on stability of Avobenzone.Sam ple P repara tion0 . 0 4 % A v ob en z on e w a s d i s p e r se d w i t h 4 . 0 % i n or g a n i c p i g m en t i n E t h a n ol .Each sam ple was irradiated (Spectr olin e UV lam ps - XX-15NB) for one week, th en centr ifug edto sep ar ate the solution from the inor ganic pigm ent.All sam ples wer e diluted to 0. 001% w/w Avob enzone based on its initially added am ou nt.Tr ansm ittance and absor bance were m easur ed usin g UV /V is spectroph otom eter (U-3010 fromH itachi).AvobenzoneOOC 4 H 9OCH 3R eferencesD ev el op m en t of T h i n - l a y er S i l i ca - coa t ed Zi n c Ox i d e a n d S u p er i or S u n sc r een s;N. Ishii, K. Wada, M. Takam a, K. Ogawa, K. J oich i and K. OhnoProceed ing XXI IFSCC Internation al Cong ress 2000, Berl in, p. 519P hotocatalytic Activity of T itanium Dioxide and Zinc Oxide;M. Kobayashi and W. KalriessCo sm etics & Toiletries, v ol. 112, n o 6, p. 831. Influ ence of U ntreated P hysical Sunscreens on the Stability of A vobenzone100806040Avobenzone and Untreated PigmentsZ1 A1R1AVOReference Pigment Avobenzone remaining Primary particleType after irradiation size (PPS) in nmAvobenzone None 100 % -R1 Rutile TiO2 < 1% 200R2 Rutile TiO2 < 1% 200A1 Anatase TiO2 < 1% 300A2 Anatase TiO2 < 1% 300Z1 Zinc Oxide < 1% 35200250 300 350 400 450 500Wavelength (nm)N o sig n i fica n t ch a n g e was ob ser v ed i n t h etr an sm ittan ce of Avoben zon e after irr adiation.Un t r eat ed t it a n iu m diox ide a n d z in c ox i dedeg raded Avobenzone.Poster A vobenzo ne - SSC N Y2001

2. Influence of Treated Titanium Dioxides on the Stability of AvobenzoneAvobenzone With Treated Anatase Titanium Dioxide1008060A1-MSA2-DSA1-SLReference Pigment Treatment Avobenzone remainingType Type after irradiationA1-SL Anatase TiO2 Silane 19%A1-MS Anatase TiO2 Methicone < 1%A2-SL Anatase TiO2 Silane < 1%A2-MS Anatase TiO2 Methicone < 1%A2-DS Anatase TiO2 Dimethicone < 1%40AVOAvobenzone With Treated Rutile Titanium Dioxide200250 300 350 400 450 500Wavelength (nm)10080R1-SLR1-DS60Reference Pigment Treatment Avobenzone remainingType Type after irradiationR1-SL Rutile TiO2 Silane < 1%R2-SL Rutile TiO2 Silane < 1%R1-MS Rutile TiO2 Methicone 38%R1-DS Rutile TiO2 Dimethicone < 1%40200R1-MSAVO250 300 350 400 450 500Wavelength (nm)Com parisons of anatase and rutile pigments after treatm ent with m ethicone, dim ethicone, and octyltriethoxysilane were m ade.Silane treatm ent: anatase A1-SL gave a better stability.Methicone treatm ent: rutile R1-MS gave a better stability.Anatase A2 had poor stability with all treatm ents.Avobenzone With Other treatments on Titanium Dioxide1008060R5-SAR4-PFReferenceR3-SCR4-PFR5-SAPigmentTypeRutile TiO2Rutile TiO2Rutile TiO2TreatmentTypeSilicaC9-15 Fluoro-AlcoholphosphateStearic Acid andAluminum HydroxideAvobenzoneremainingafter irradiation76%28%3%P.P.S.(nm)90300154020R3-SCAVOOther treatm ents were also evaluated. The silica treatedtitan ium dioxide (R3-SC) g ave the best stability.0250 300 350 400 450 500Wavelengt h (nm)3. Influence of Treated Zinc Oxides and Iron Oxides on the Stability of Avobenzone10080604020Avobenzone With Zinc OxideZ3-MSZ4-SLZ1-SCZ2-SCAVOReference Pigment Avobenzone remaining Primary particleType after irradiation size (PPS) in nmZ2-SC Silica 49 % 25Z1-SC Silica 18 % 35Z3-MS Methicone < 1% 25Z4-SL Silane 3 % 120Treated zinc oxides were evaluated. Avobenzone ismore stable with the presence of Silica treated ZnO.0250 300 350 400 450 500Wavelength (nm)Po ster A vo benz one - SSC N Y2001

ReferenceTreatmentTypeAvobenzone remainingafter irradiationAvobenzone with Iron OxidesRED-SLYEL-SLBLK-SLSilaneSilaneSilane97 %< 1 %< 1 %10080YEL-SLBLK-SLAvobenzone may also be form ulated in make-up products.We evaluated several grades of Iron Oxides, in order todetermine if these pigments would impair the activity ofAvobenzone. Red iron oxide was found to have a negligibleeffect on the stability of Avobenzone, while yellow andblack iron oxides, on the contr ary, lead to a com pletedegradation of Avobenzone.6040200RED-SLAVO250 300 350 400 450 500Wavelength (nm)ConclusionIn the course of this study, we have shown that Avobenzone, when combined with uncoated physicalsunscreens, retains little activity following irradiation.We also dem onstrated that the surface treatm ent of pigm ents could lim it this degradation, and in thebest case of silica treated Titanium diox ide R3-SC, 76 p er cent of the activity was retained.Additional measurements are needed to better understand the UV properties of combinations of Avobenzoneand inorganic pigments. Work is in progress in our laboratories to determine the influence of the followingparameters :Pigm ent type and m orphology;Extent and type of surface treatment;Particle size of the pigm ent.The results will need to be correlated with approved m ethods for testing sunscreens form ulations.AcknowledgmentThe a uth ors want to th ank Dr. Yun Sh ao for h is tech nica l contribution and Dr. Pascal Delrieu for h istechnical contribution and his art work on this poster.Reference Codes and Trade Nam es of Pigments used in this study :Reference codeA1A1-SLA1-MSA2A2-MSA2-DSR1R1-SLR1-MSR1-DSR2R2-SLTrade nameCTFA328BTD-11S2BTD-MS2TiO2 FF PHARMATIO2 FFP-MS2TIO2 FFP-DS4Tronox CR-837RBTD-11S2RBTD-MS2RBTD-DS4CR-834RBTD-834-11S2Reference codeR3-SCR4-PFR5-SAZ1Z1-SCZ2-SCZ3-MSZ4-SLBLK-SLRED-SLYEL-SLTrade nameMAX LIGHT TS-04PF-5 TIO2 CR-50TTO-51-CZNO-350ZNO-350 SIO2(5)MAX LIGHT ZS-032ZNO XZ-MS4A120-ZNO-11S3BBO-11S2BRO-11S2BYO-11S2Poster A vobenzon e - SSCN Y2001