DETERMINATION OF 1,4-DIOXANE 335 H30 + R--(OCH•CH)•OSO 3- 4- H•O ß R--(OCH2CH2)•OH 4- H + 4- SO4= Under suitably acidic conditions this reaction is thus autocatalytic, and in addition can lead to the generation of additional dioxane by acid catalyzed cleavage and cyclization of the polyoxyethylene moiety. In order to assess the importance of these reactions in the present analytical method, samples of FAES were analyzed after addition of 0.1% iN KOH or 0.1% H3PO 4. The results are shown in Table III. The basic sample gave a very reproducible level of dioxane, while the acidic sample gave much higher and more erratic results. In analyzing this type sample, therefore, it is essential that the sample be made basic before injection to prevent formation of additional dioxane. We have attempted to correlate the present method with the vacuum distillation method of Birkel et al. Two samples of FAES analyzed by the present method showed 1,4-D levels of 73 + 3 ppm and 81 + 3 ppm, as compared to levels of 48 ppm for each by the method of Birkel. This discrepancy may be due to a low recovery of 1,4-D from this particular surfactant, as was noted by Birkel in his work on polysorbates. It may also be that the FAES was undergoing slow hydrolysis with generation of 1,4-D, as our results were obtained approximately 2 months after the vacuum distillation analyses were performed. We are currently reana!.•zing these samples at intervals in an attempt to resolve this point. METHANOL POLYOXYETHYLEN E DIST EARATE 50% (W/V) IN METHANOL 20.ul DIRECT INJECTION D I OXAN E Figure 6. Typical chromatogram for polyoxyethelene distearate.

336 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Direct injection known addition data Sample Amount Added Amount Found % Recovered FAES (A) x 0 ppm 1013 ppm n/a 1000 2023 101.0 FAES (B) • 0 341 n/a 250 571 92.0 PEG-ds • 0 199 n/a 400 615 104.0 •FAES = Fatty Alcohol Ethoxy Sulfate 2PEG-ds = PEG-150 Distearate VACUUM STRIPPED FAES 20pl DIRECT INJECTION A- NEAT, ,,-, 0.2 ppm DIOXA B-SPIKED WITH 0.Sppm Figure 7. Typical chromatograms of a vacuum-stripped FAES sample. Table III Effect of pH • (sles) Condition ppm Found Basic 341 Acidic 688 + artifacts X(Direct Injection)