548 JOURNAL OF COSMETIC SCIENCE Table II Antimicrobial Activity, Measured by Zone Inhibition, of Triclosan and Solubilizing Agents Diameter of inhibition zone (mm) Compound E. coli P. aeruginosa S. aureus A. niger C. albicans Triclosan powder 18.8 No zone 19.5 17.4 14.5 N-methylglucamine 15.9 19.3 14.3 25.5 20.9 L-arginine No zone 14.7 No zone 24.6 20.1 Ethanolamine 23.9 24.6 12.9 27.8 18.4 SLS No zone No zone 18.2 28.6 15.1 [3CD No zone No zone No zone No zone No zone for mixtures of triclosan and the solubilizing agents prepared in water or the pH 7.4 phosphate buffer. In Table III the results for the phosphate buffer solutions are listed. The diameters of the zones of inhibition increased when a constant concentration of 6.0 mg/ml -• of triclosan was mixed with all the solubilizers. This showed that the bacte- riostatic efficacy of triclosan increased when combined with the solubilizers. Whether this was because of the bacteriostatic efficacy of the solubilizer, or a synergistic effect that occurred, is unknown. The results listed in Table III show that, on average, the combined solutions doubled the diameters of the inhibition zones. From these results, it is also clear that N- methylglucamine, L-arginine, and ethanolamine in combination with triclosan were the most effective antimicrobial combinations. Although not as effective as the other solu- bilizers, both [3CD and SLS also enhanced the growth inhibition of most of the organ- isms tested when combined with triclosan. The difference between the antimicrobial activity of solutions containing the complexing agents, N-methylglucamine, L-arginine, and ethanolamine, and the compounds that encapsulate the triclosan, [3CD and SLS, was significant. This difference could be the result of partial inactivation of the triclosan by miceliar entrapping on inclusion because these processes reduce the amount of free triclosan available in solution. Overall, triclosan/solubilizer combinations were most effective against A. niger and least effective against P. aeruginosa. CONCLUSIONS A solubilization study for triclosan in water and pH 7.4 phosphate buffer at 30 ø C Table III Antimicrobial Activity, Measured by Zone Inhibition, of Solutions Prepared in pH 7.4 Phosphate Buffer Containing Triclosan and Solubilizing Agents Diameter of inhibition zone (mm) Compound E. coli P. aeruginosa S. aureus A. niger C. albicans N-methylglucamine 34.2 17.4 32.7 42.4 29.4 L-arginine 34.9 19.1 34.1 44.2 31.4 Ethanolamine 35.0 23.5 31.5 42.5 31.2 SLS 23.5 12.4 21.0 30.4 23.2 •CD 30.5 No zone 23.1 27.8 27.2

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