DIRECT ANALYSIS OF DIMETHICONE IN AQUEOUS EMULSIONS 215 concentrations while still in aqueous emulsions. This rapid method of analysis will be helpful in quality testing to support manufacturing and stability testing of products that contain dimethicone emulsions. Direct analysis of samples without sample preparation is appealing compared with more lengthy, complex methods. Of course, as with all new analytical procedures, this method should be validated on a product-by-product basis because other ingredients and excipients could potentially interfere with this procedure. ACKNOWLEDGMENT This work was supported b y the Center for Chemical Technology at Weber State University. REFERENCES (1) “Dimethic one,” Toxic o logy Data Network, U.S. National Library of Medicine, accessed April 8, 2019, https://toxnet.nlm.nih.gov /cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+1808. (2) P. K. Farris, “Topica l Skin Care and the Cosmetic Patient,” in Master Techniques in Facial Rejuvenation, (Elsevier Health Sciences, Atlanta, GA, 2018), pp. 68–72. (3) E. S. Ihde, J. R. B os camp, J. M. Loh, and L. Rosen, Safety and effi cacy of a 100% dimethicone pedicu- locide in school-age children, BMC Pediatr., 15, 70–76 (2015). (4) J. Heukelbach, D. P il ger, F. A. Oliveira, A. Khakban, L. Ariza, and H. Feldmeier, A highly effi cacious pediculicide based on dimethicone: randomized observer blinded comparative trial, BMC Infect Dis., 8, 115–124 (2008). Table IV Effect of Various Excipients on Method 2 Assay Results Excipient added Excipient conc. (%) Dimethicone % averagea (n = 3) RSD (%) Control 0.00 3.01 0.51 Laureth-4 0.30 2.96 1.60 0.60 3.02 2.32 Laureth-23 0.30 3.05 1.68 0.60 3.06 1.68 Triton X-100 0.30 2.95 1.55 0.60 3.03 2.70 PPG-15 stearyl ether 0.30 3.00 2.03 0.60 3.01 2.03 PEG-100 stearate 0.30 3.01 2.82 0.60 2.95 1.74 Sorbitan laurate 0.30 3.02 2.82 0.60 2.95 1.60 Methylparaben 0.05 2.99 1.65 0.10 2.99 0.84 Propylparaben 0.05 3.01 0.96 0.10 3.00 1.17 Phenoxyethanol 0.05 2.99 0.67 0.10 3.00 1.07 DMDM hydantoin 0.01 3.00 1.68 0.02 3.02 1.15 Kathon 0.0050 2.97 0.19 0.0100 3.00 1.39 Sodium benzoate 0.05 3.01 1.45 0.10 3.00 1.15 a Actual dimethicone concentration in all samples = 3.00% (g/100 g) .

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