A novel GC-FID method for quantification of residual 1,4-Dioxane and Ethylene Oxide at ppm levels in ethoxylated surfactants

Fatty alcohol ethoxylates represent an important group of nonionic surfactants that can act as emulsifiers, dispersants, detergents, and humectants, as well as fixing agents and co-surfactants. Throughout the ethoxylation process, residual monomers and toxic impurities with carcinogenic potential may be present, such as ethylene oxide and 1,4 dioxane. Consequently, regulatory agencies are constantly lowering the limits of the residual levels of those contaminants. For instance, the US State of New York limited the 1,4-dioxane to ppm levels in household cleaners, personal care, and cosmetic products. Due to the very low limits being more and more requested, most analytical methods currently require the use of a mass-spectrometer integrated chromatograph (GC-MS). This work presents the development and validation of a fast, easy-to-perform, low-cost method with reduced solvent use by Headspace gas chromatography with flame ionization detector for determination of low levels of ethylene oxide and 1,4-dioxane in ethoxylated fatty alcohols. The method was validated in terms of selectivity, linearity, accuracy, precision, limit of quantification, limit of detection, and robustness. The analytical curve was constructed in 6 levels, i.e., 0.5, 1.0, 2.0, 3.0, 4.0, and 5.0 ppm, with a coefficient of transparency and determination above 0.990, meeting all the acceptance criteria and statistics determined for linearity. Additionally, the presented method is robust, selective, and with LoQ of 0.5 ppm. The accuracy (80-110) and precision (<11%) were considered adequate and in accordance with the principles established by the AOAC. Thus, the newly developed and validated method proved to be adequate, reliable, and reproducible for the determination of EO and 1,4-dioxane in liquid alcohols with different degrees of ethoxylation, as well as easy to implement in quality control laboratories, due to its easiness, fastness, low cost, and complexity, eliminating the need of a GC-MS.