Ensuring Traceability Using qNMR in the Quantitative Analysis of Formaldehyde and Acetaldehyde

Currently, indoor air quality guidelines for formaldehyde and acetaldehyde are set by the Ministry of Health, Labour and Welfare of Japan. Aldehydes are widely used in adhesives and preservatives, and exposure to these compounds via indoor air is a matter of concern. Considering that contact with indoor air is part of daily life, evaluation of indoor air quality is extremely important. 2,4-Dinitrophenylhydrazine (DNPH) derivatization is widely used for quantitative analysis of aldehydes. A certified reference material with traceability to the International System of Units (SI) is required for this method. However, currently, there are no certified reference materials available for aldehyde-DNPH derivatives, which means that the quantified values obtained by this method are not sufficiently reliable. In this study, we determined the actual content and purity of commercially available aldehyde-DNPH derivatives using H-1-quantitative NMR (qNMR), which can be measured with SI-traceability. Although the commercial DNPH derivatives of formaldehyde and acetaldehyde were low concentration solutions, we were able to determine their purities using H-1-qNMR. Furthermore, we were able to separate and quantify the acetaldehyde isomers generated by the derivatization reaction. In conclusion, it is possible to obtain highly accurate results using H-1-qNMR with commercially available reagents that are not certified metrologically.