IDENTIFICATION OF PRESERVATIVES 79 be the preservative. The spots should be outlined with a spatula for future location. A tank containing a few crystals of iodine was warmed and the fie plate was placed into the 1.2 vapors. Formation of brown spots will indicate the presence of organic compounds. The spots should be outlined for future location, as the iodine will gradually disappear. The same fie plate and/or additional plates was sprayed evenly with suggested spray reagents. Additional plates must be developed if more than one spray reagent is used, as the reagents form stable chemical derivatives. Rs's for the located spots were calculated as follows: distance of spot center from start point Ill = distance of solvent front from start point Results were then compared with standards to identify the preservative. PtESULTS AND DIscussioN A total of 26 perservatives were examined by the described procedure, with the results shown in Table II. All preservatives except dimethoxane were de- tectable by one or more of the visualization procedures. The Rf values given Table III Results of Adding Preservatives to a Commercial Shampoo Rr Preservative Standard Shampoo Detected by Butylated hydroxytoluene 0.85 0.86 I,, Carvacrol 0.67 0.66 I,_, p-Chloro-m-xylenol 0.59 0.58 I,_, Chlorhexidine acetate 0.59 0.60 I,_, 4-Chloro-3-methyl phenol 0.60 0.61 I,, Dehydroacetic acid 0.26 0.26 UV Dichloro-m-xylenol 0.70 0.72 I,_. Dichlorophene 0.53 0.55 UV, I_o Fluorsalan 0.54 0.57 UV Gcrmall 115 0.00 0.00 I, Reagent C Hexachlorophene 0.35 0.33 UV, Irga,'an CF:• 0.64 0.65 UV Irgasan DP 300 0.68 0.68 UV o-Phenylphenol 0.76 0.75 UV, Propylparaben 0.55 0.56 UV, I2 Resorcino] 0.24 0.26 UV, Salicylani]ide 0.73 0.74 UV, T• trabromo-o-creso] 0.64 0.65 UV, very faint Tribromsalan 0.60 0.60 UV Trichlocarban 0.66 0.66 UV Vancide 89 RE 0.81 0.81 Reagent C Zinc pyrithione 0.78 0.76 UV, Is

8J JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table IV Identification of Preservatives in Commercial Cosmetic Products ............................. Lotion Lotion Cream Rr Br Rr Preservative Standard Sample Standard Sample Standard Sample Pffrabdn• 0.60 0.62----- 0.64 0.67 0.57 0.60 p-Chloro-m-xylenol 0.66 0.67 0.69 0.69 0.60 0.60 Tetrabromo-o-cresol ...... 0.78 ...... Irgasan DP 300 0.81 0.82 0.78 0.78 (•.• 0.74 Dehydroacetic acid 0.15 0.17 ...... 0.27 0.24 Table V Tlc of Cosmetic Products with Known Preservatives Cosmetic Product Preservative Claimed Found Deodorant soap Deodorant soap Deodorant soap Deodorant soap Deodorant soap Deodorant soap Shampoo Hand lotion Deodorant soap HCP ø, Tribromsalan Tribromsalan, Trichlocarban, Irgasan CF-3 Tribromsalan HCP •, Trichlocarban HCP ø HCP • Dehydroacetic acid Propylparaben Tribromsalan, Irgasan DP 300 Tribromsalan Tribromsalan, Trichlocarban, Irgasan CF-3 Tribromsalan Trichlocarban Dehydroacetic acid Propylparaben Tribromsalan, Irgasan DP 300 See text for discussion. Table VI Limit of Detectability of Several Preservatives Preservative UV L (t•g) (t•g) Reagent A Tribromsalan 0.1 0.1 Hexachlorophene 0.5 0.1 faint Propylparaben 0.1 0.1 Trichlocarban 0.1 ... Dehydroacetic acid 0.5 ... p-Chloro-m-xylenol 0.5 0.1 Tetrabromo-o-eresol 0.5 2 faint 015 violet - 0.5 pink ß ß , 0.5 blue