SAFETY EVALUATION OF AN OPHTHALMIC SOLUTION 71 REFERENCES (1) B. Ballantyne and D. W. Swanston, Ocular Irritation Tests, Br.J. Pharmacol., 46, 577 (1972). (2) E. V. Buehler and E. A. Neuman, A comparison of eye irritation in monkeys and rabbits, Toxicol. Appl. Pharmacol, 6, 701 (1964). (3) I. F. Gnant and K. H. Harper, The potential irritancy to the rabbit eye mucosa of certain commercially available shampoos, J. Soc. Cosmet. Chem., 15,290 (1964). (4) F. N. Marzulli and M. E. Simon, Eye irritation from topically applied drugs and cosmetics: preclinical studies, Amer. J. Optom., 48, 61 (1971). (5) E. C. Darges, S. R. Kynoch and M.P. Liggett, Eye irritation tests an assessment of the maximum delay time for remedial irrigation, J. Soc. Cosmet. Chem., 27, 301 (1976). (6) Code of Federal Regulations, Tests for eye irritants. Title 16, Section 1500.42 (1973). (7) J. H. Beckley, Comparative Eye Testing: Man vs Animal, Toxicol. Appl. Pharmacol., Supplement 2, 93 (1965). (8) N.J. Van Abbe, Eye irritation: studies relating to responses in man and laboratory animals, J. Soc. Cosmet. Chem., 24, 685 (1973). (9) McDonald & Shaddeck, Marzulli & Maibach, Eds., "Dermatotoxicology and Pharmacology, Hemisphere Publishing: Washington, 1977 Chapter 4.

j. Soc. Cosmet. Chem., 30, 73-79 (March/April 1979) The analysis of 2,2'-dithiobis-pyridine-l,l'.dioxide and related compounds in clear antidandruff shampoos via reverse-phase liquid chromatography ROBERTJ. FENN and DAVID A. CSEJKA Olin Research Center, 275 [F inchester Ave., New Haven, CT 06511. Received August 8, 1979. Synopsis A REVERSE-PHASE LIQUID CHROMATOGRAPHIC METHOD is described for the ANALYSIS of 2,2'-DITHIOBIS-PYRIDINE-I,I'-DIOXIDE (I) and related compounds in some CLEAR ANTIDANDRUFF SHAMPOO formulations. Other compounds simultaneously quantitated are: 2-pyridinethiol, 2-pyridinesulfonic acid and 2-pyridinesulfonic acid 1-oxide. Another related compound, 2,2'-dithiobispyridine, is analyzed separately. The analysis of (I) offers increased precision and accuracy and decreased analysis time compared to the commonly used polarographic method. In addition, some of the other compounds of interest cannot be conveniently analyzed polarographically, but are easily quantitated by liquid chromatography. INTRODUCTION The magnesium sulfate adduct of 2,2'-dithiobis-pyridine-l,l'-dioxide (OMADINE © MDS Registered Trademark of Olin Corp., Stamford, Conn.), is an excellent antimicrobial agent and is presently used as an antidandruff ingredient in numerous clear shampoo formulations. A typical concentration of 2,2'-dithiobis-pyridine-l,l'- dioxide (OMDS) is 1%. A fast, accurate analytical method for the analysis of this compound is of obvious interest, both as a quality control tool and as a means of determining its stability in various formulations. Particularly since applications are in personal care products such as shampoos, the analysis of the commonly known degradation products of OMDS is also of interest. These compounds include 2-pyridinethiol-l-oxide (OM), 2-pyridine- thiol (2MP), 2,2'-dithiobis-pyridine (PDS), 2-pyridinesulfonic acid 1-oxide (OMSA) and 2-pyridinesulfonic acid (PSA). With regard to specific analytical methods for these compounds, the most commonly used at present are polarographic (1-3) iodimetric (4) and, in the case of OM, colorimetric (5). In this laboratory polarographic methods have, until recently, been used almost exclusively. Several problems are encountered with these methods, 73