ENCAPSULATED PERFUMES 657 Table I Typical Particle Size Distribution of (•-CAP Per Cent Through 200 mesh 99 Through 230 mesh 97 Through 270 mesh 80 Through 325 mesh 70 Once the physical compatability properties had been determined, at- tention was focused on the performance of the encapsulations. From the onset of the project the services of perfumers were employed to evaluate the odor-release characteristics of the encapsulatd perfume in various products over a period of time. In addition, perfumed, aerosol antiper- spirant samples were also provided for subjects who were questioned carefully as to their observations after extended usage. Although the subjective assessment of the functionality of the encapsulated perfume was convincing, a more objective means to measure the fragrance release of the encapsulated perfume both in vivo and vitro was sought. An analytical procedure was developed based on gas-liquid chroma- tographic analysis of vapor samples withdrawn from treated areas. Con- siderable difficulty was initially encountered with quantitative determi- nations because of the large variety of materials present in the normal perfume composition. The vapor pressures and the concentrations of most chemicals used in perfumes are too low for accurate quantitative detection in a small vapor sample. Therefore, materials were chosen for encapsulation that have a high enough vapor pressure to make detection and measurement relatively easy. An additional requirement of rapid elution in the gas chromatograph to enable us to perform an analysis every 15 min is fulfilled by these high-vapor-pressure materials. A representative selection of materials was made from those commonly found in perfume compositions. This selection included hydrocarbons, alcohols, esters, and ethers. The encapsulation of these single materials was identical to the encapsulations of normal perfume compounds con- taining multiple components. These encapsulations were incorporated in a representative aerosol antiperspirant product made according to the formulation in Table II. This formulation provides a net 1% level of encapsulated perfume in the finished can, which represents the highest levels of encapsulated perfume tested. When lower levels were used, the balance was made up with isopropyl myristate.

658 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Antiperspirant Fornmlation Concentrate Per Cent by Weight l. lsopropyl myristate" 55.45 2. Cab-O-Sil M-5 b 3.64 3. Aluminumchlorhydrate a 31.82 4. Q-CAP perfumec 9.09 Fill Concentrate 11.00 Propellants (50: 50) 11/12 89.00 Wickhen Products, Inc., Huguenot, N.Y. Cabot Corporation, Boston, Mass. Registered trademark of Polak's Frutal Works, Inc., Middletown, N.Y. Figure 2. Sampling device and syringe Control samples were also prepared using corresponding unencapsu- lated.liquid materials in the same formulation. Depending upon the spe- cific vapor pressure of the material involved, a variety of dosages were