Precise measurement of 1,4-dioxane concentration in cleaning products: A review of the current state-of-the-art

Abstract: 1,4-Dioxane, a co-product that forms during the preparation of ethoxylated surfactants, particularly sulfated and phosphorylated ethoxylates, is classified as a potential human carcinogen whose occurrence in surface water and groundwater is of particular concern. As a result, the U.S. state of New York has passed laws that will limit the concentration of 1,4-dioxane to ppm levels in household cleansing, personal care and cosmetics products, all of which commonly employ ethoxylated fatty alcohol sulfate surfactants and California is considering such laws. This review first assesses the methodologies used to quantify 1,4-dioxane in surface water and drinking water, then extends the assessment to commercially available products, which are more complex sample matrices than water. Our assessment indicates that gas chromatography using conventional capillary columns and mass spectrometric (MS) detection, and the employment of an internal standard, particularly 1,4-dioxane-d₈, is the best approach. A means of isolating and concentrating 1,4-dioxane from the commercial samples is critical to achieve resolution at the sub-ppm level and to minimize interference from contaminants present in the sample matrix. We review the different concentration approaches, such as headspace analysis, liquid-liquid and solid-phase extraction, purge-and-trap, and solid-phase microextraction, and evaluate their advantages and disadvantages for the robust long-term assessment of 1,4-dioxane levels in commercial products.