Primary oxidation products affect the quantification of formaldehyde in autoxidized fatty alcohol ethoxylates when using DNPH derivatization

Non-ionic surfactants, e.g. fatty alcohol ethoxylates, are considered to cause less skin irritation than other types of surfactants. However, the autoxidation of alcohol ethoxylates generates products that are both skin irritating and sensitizing, such as formaldehyde. It has been suggested that formaldehyde be used as an indicator of the degree of autoxidation of fatty alcohol ethoxylates, and thus also as an indicator of the sensitizing capacity of the product. Attempts to analyse formaldehyde in autoxidized ethoxylates using 2,4-dinitrophenylhydrazine derivatization resulted in formation of the corresponding hydrazone not only from free formaldehyde but also from autoxidation products during the derivatization reaction. Consequently, this derivatizing agent is inappropriate for the determination of formaldehyde in autoxidized fatty alcohol ethoxylates. Focus on the content of primary oxidation products, i.e. hydroperoxides/peroxides, is suggested, particularly as they also are potent sensitizers.