DETERMINATION OF HEXACHLOROPHENE 689 :• .•.•. •' "..•' i'•l•?• :• ., • ' :•" •:_• .... ....... ....... -? ..... • :: .•. :: • ,•. • Figure 3. Gas-liquid chromatographic standard cu•e Using the same data as were used in the standard curves, we may ob- tain a measure ot• the reproducibility ot• the silylation. The peak ratio/ rag, P, is given by where R = peak height of hexachlorophene divided by peak height of DCHP internal standard and W = weight of hexachlorophene in mg The results of these calculations are given in Table I. It can be seen that the reproducibility is quite adequate. In the range of. 1-5 mg the co- efficient of variation is 2.8% and in the range of 0.2-0.5 mg it is 2.1%. Retention Index The Kovats retention index (6, 7) o.n the SE 30 column at 250øC was obtained using the straight-chain aliphatic hydrocarbons Cv2, C.,4, C.,8, and Ca•. The retention index was found to be 2804.

690 .JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ..... I • i I ] [ '• I ' ]•l• [ I I • I I ' .... Figure 4. Comparison of extraction methods Comparison Between the Base-Acid Extraction and the Acetonitrile- Hexane Method Figure 4 shows the GIJC recording of a co.mplex mixture after iso- lation by the two methods. While there is little interference from ex- traneous materials after acetonitrile-hexane, there is none after the base- acid extraction. The superiority of the base-acid extraction was ob- served with several formulations. The base-acid extraction method was selected for use because of its freedom from extraneous peaks. The ace- Ionitrile-hexane method is presented for its simplicity and may be used when interferences are known to 1)e absent. Recovery o[ Added Hexachlorophene Salnples of four marketed products were assayed for hexachlorophene. To aliquots of these an amount of hexachlorophene roughly equal to the amount present was added and the materials were then reassayed (Table II). Recoveries were essentially quantitative, the lowest being 95.5%. IIexachlorophene was added to three products not already containing this substance: talc, white ointment (U.S.P., a hydrocarbon beeswax corn-