This document specifies a method for the determination of the amount of selected carbonyl compounds (formaldehyde and acetaldehyde) as their 2,4-dinitrophenylhydrazones in vapour product emissions using reversed phase liquid chromatography coupled with Ultraviolet or Diode Array detector (LC-UV or LC-DAD). This document does not include the analysis of other carbonyl compounds, such as acrolein and crotonaldehyde, due to previous work indicated issues associated with stability of these compounds and inconsistencies in deliveries of these compounds in emissions from vapour products [6].