ENCAPSULATED PERFUMES 659 .' :. -:• ß .• :•v*•- ....... :'•' • :: .: ... , - •... ..., . 'i . Figure 3. In vitro sampling apparatus .'½ . ... .. :..... used in the finished aerosol samples. (These dosages ranged from 0.4 to 1.0% for the encapsulation with an equivalent range of 0.2 to 0.5% for the unencapsulated oil.) Aerosol samples, prepared as previously de- scribed, were applied to either silicone rubber pads, for in vitro tests, or to the axillary region of a human subject, for in vivo tests. A sampling device was developed to entrap the perfume vapors above the axillary region consisting of a copper cylinder, 11/2 in. in diameter and 3 in. long, with a silicone septum at the closed end, and having a volume of 100 cc (Fig. 2). In practice, the open end of the cylinder is placed over the tested region for 60 sec, as shown in Fig. 3, and then a vapor sample is withdrawn into a 10-cc gas-tight hypodermic syringe equipped with a 3-in., No. 22 needle, also shown in Fig. 2. A 3-ft, 1/4-in. o.d. copper column filled with 2.0% Apiezion M* on 60 * Apiezion M is available from Jamcs G. Biddle Co., Plymouth Meeting, Pa.

660 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS to 80 mesh Chromosorb W • is used at a temperature of 150øC and a he- lium flow rate of 80 cc per minute. In order to achieve maximum sensi- tivity, a flame ionization detector is employed. The 10-cc vapor sample is mostly air which causes extinction of the flame in the detector. The lat- ter has to be reignited for each sample. The relative concentration of the organics in the vapor sample is determined by measuring its peak height. During the course of a particular test it is necessary to have the sub- ject perspire in order to release the perfume. This is best accomplished by "heating" the subject with the aid of an electric blanket and sitting on an electric heating pad. The sipping of hot tea by the subject also facili- tates perspiration. Another technique, again based upon gas-liquid chromatography, was developed in order to measure water vapor caused by the perspiration of the subjects. A 3-ft, 1/4-in. o.d. copper column with 50% Carbowax 20Ml' on 60 to 80 mesh Chromosorb W is used with a helium flow rate of 10 cc per minute at 130øC. The unusual 50% substrate is a development that allows water vapor to be quantified since it gives symmetrical peaks. The high liquid ratio lessens adsorption phenomena. A thermal-conduc- tivity detector is used since the hydrogen flame detector is insensitive to water vapor. The same sampling device is used and again it is allowed to equili- brate for one minute in the axillary region. A 10-cc smnple is taken, again utilizing a gas-tight hypodermic syringe. The water vapor in the air due to atmospheric humidity gives us a background reading. As the subject perspires, the water vapor reading obtained in the gas chromatograph increases to a maximum. After the subject perspires for a given time and cooling is desired, the electric blanket and electric heating pad are removed. A marked reduction in the axillary water vapor is subsequently observed. RESULTS AND DISCUSSION The purpose of the analytical procedure was to obtain objective, quantitative data on the performance of encapsulated perfumes in aerosol products. Our original oilactive observations described the performance of the encapsulated perfumes as having sustained release, delayed release, and maintainence of freshness. The initial in vitro tests confirmed that repeated release of volatiles from the encapsulated perfume did occur. The results shown in Fig. 4 * Chromosorb W is available from Arialabs, Inc., Hamden, Conn. t Carbowax 20'M is available from Union Carbide, New York, N.Y.