DETERMINATION OF HEXACHLOROPHENE 687 lrigu. re 1. Gas-liquid chromatogram of 12 t•g of hexachlorophene Le[t: Silylated. Right: Not silylated RESULTS AND DISCUSSION Effects o[ Silylation on Gas-Liquid Chromatography o[ Hexachlorophene On the right side of Fig. I is the gas-liquid chromatographic record of an injection of 12 vg of hexachiorophene and 4 vg of DCHP. On the left side of the figure is the GLC of the same amount of material after silylation. It can be seen that the silylation eliminates the extensive tail- ing and thus increases the peak height by more than tenfold. The re- tention time of the silylated compound is essentially unchanged. In Fig. 2 the same phenomenon is seen with one-tenth the concentration of hexachlorophene and DCHP. Here we may see the appearance of small peaks from other components in the injected mixture that were not evi- dent at the higher attenuation. An amount as low as 0.1 t•g of hexa- chlorophene when silylated would be readily detected. This detection limit compares favorably with that of 5 vg obtained by Porcaro with a flame ionization detector (4). Standard Curve and Reprod•tcibility o[ Silylation In this experiment 0.2 to 5 mg of hexachlorophene in the presence of 2 mg of DCHP internal standard is treated with 1.0 ml of silylation agent. The standard curves are presented in Fig. 3. Two ranges are presented separately: 0-5 mg/ml and 0-0.5 mg/ml. The curves shown are the least squares lines of best fit. Very satisfactory linearfry is obtained.

688 .JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 2. Gas-liquid chromatogram of 1.2/•g of hexachlorophenc Left: Silylatcd. Right: Not silylatcd Table I Reproducibility of $ilylation of Hexachlorophene Hexachlorophene, mg/ml Peak Ratio a Peak Ratio/mg 4.994 1.816 0.3636 4.042 1.434 0.3547 3.080 1.132 0.3679 2.018 0.7596 0.3764 1.036 0.3638 0.3511 0.4994 1.7305 0.4042 1.3521 0.3080 1.0400 0.2018 0.6657 0.3627 0.0102 0.3464 0.3345 0.3376 0.3299 0.3371 0.007 Ratio of hexachlorophene peak to dicyclohexylphthalate internal standard peak.