INGREDIENT RELEASE FROM AEROSOL FILMS 679 reduced to 0.45%. In order to accelerate the release in quantities suf- ficient for detection, 0.45% of sodium chloride solution was used instead of 0.9% for these studies. Further, it was noted that due to some complex formation of Gentian Violet with the polymer, an optimum concentration of Gentian Violet had to be maintained in the polymeric fihn so that the amount being released could be measured over a reasonable period of time. It was found that films cast from polymeric solutions containing 0.2% w/w of Gentian Violet were best suited for the release studies. All of the data presented in this study show that the release of Gentian Violet follows first-order kinetics according to the following equation: log A - 2.303 -1- log A0 Figure 2 illustrates the effect of different solvent systetns on the rate of release of Gentian Violet from Emerez 1533 containing 10% hexadecyl alcohol. It can be noted from these plots that the rate of release for various solvent systems does not change appreciably from one another but remains relatively constant. This indicates that the release is not influenced by either a shift in pH or the ionic species of the solvent sys- tem. The screening of fihns on the basis of the release of Gentian Violet resulted in the selection of Polymid 1155 fihns because these films did not exhibit any pronounced tendency towards complexation. It is therefore evident that some substances are weakly bound by the Polymid 1155 fihn and strongly bound by other films such as Emerez 1533, 1536, and 1540. The magnitude of binding is also influenced by the number of binding sites available in the polymer structure for the interaction with Gentian Violet. For the release to be exponential, the plot of log ,4 versus time, at zero time, should correspond to log ,40 but the typical apparent first- order profiles show that the values of y intercepts are, in fact, less than the predicted values. The plots seem to indicate that one portion of the compound is released immediately and the other portion exponentially. The initial release is faster than the remainder which follows first-order kinetics. This may be attributed to the presence of some compound on the surface of the film which may be ignored. There is, therefore, a time lag before the rate follows a first-order process. Hence, the linear portion of the curve is the rate-determining step for the release. Since the rate release during the first 60 minutes (time lag) was indeterminate, the rate-limiting step permitted the determination of relative rate con- stants and half life for Gentian Violet in various fihns as shown in Table

680 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table V Rate of Release and Half Life of Gentian Violet from Selected Films Film Rate Desorbing Constant t•/.o• Plasticizer (%) Solution • Slope K, hr -• hr Emerez 1533 Hexadecyl alcohol (10) A Emerez 1533 Hexadecyl alcohol (10) B Emerez 1533 Hexadecyl alcohol (10) C Emerez 1536 ... A Emerez 1540 Hexadecyl alcohol (30) A Emerez 1540 Citroflex-4 (10) A Emerez 1540 Amerchol L-101 (10) A Polymid 1155 Hexadecyl alcohol (10) A Polymid 1155 Citroflex-4 (10) A Polymid 1155 Amerchol L-101 (10) A Carboset 525 ... A 65 71 75 40 50 1 9 1 9 27 23 1.2 1.9 X 10 -s 1.50 X 10 -2 46 X 10 -a 1.63 X 10 -2 42.5 X 10 -3 1.73 X 10 -2 40 X 10 -3 9.20 X 10 -a 75 X 10 -s 1.15 X 10 -'ø' 60 X 10 -3 4.30 X 10 -3 161 X 10 -3 4.30 X 10 -s 161 X 10 -2 6.10 X 10 -2 11.7 X 10 -2 5.30 X 10 -2 13 X 10 -2 2.76 X 10 -2 25 X 10 -a 4.30 X 10 -3 161 • A, 0.45% sodium chloride in demineralized water B, 0.45% sodium sulfate (anhydrous) in demineralized water C, potassium phosphate buffer, pH 7. V. The first-order rate constant, h, was calculated from the slope of the linear plot according to' and the half life, K = --slope X 2.303 t•/•= 0.693/k. Gentian Violet was found to be a good substance to use as a model for release studies. Other substances are currently under investigation in order to determine their release from these films. SUMMARY AND CONCLUSIONS A study was made of several films which were evaluated on the basis of their alkali resistance, film hardness, and modulus of elasticity. The effect of various plasticizers upon these properties was also noted. Based upon these results, aerosol formulations were prepared and evalu- ated in order to determine the suitability of each of the combinations for future application as a spray. Gentian Violet was incorporated into solutions of the film-forming agents and films were cast. The rate of release of Gentian Violet from these films and the effect of electrolytes upon this release were noted. This release was determined using a specially developed apparatus and method.