Changes of the storage stability of ketones collected on activated coconut carbon in environmental ketone measurement

: The storage stability for six ketones was studied on four activated coconut carbons commonly used for air sampling in Japan. As the ratios of the enol form of cyclohexanone and methyl ethyl ketone are high, the ketones showed drastic losses during storage (storage stability), which could be attributed to catalytic oxidation and chemisorption. Moreover, adsorbed water caused a further decrease in recoveries of the ketones from the carbons. Because keto-enol tautomerism and hydration are catalyzed by acid or base, the relationships between the recoveries of the ketones from the carbons and pH in the aqueous solution of the carbons and the ignition residue of the carbons were investigated. As a result, the intensity of acidity or basicity of the carbons correlated with the loss of the ketones during storage, but the ignition residue of the carbons did not. Therefore, these results lead us to the conclusion that a more neutral coconut carbon is more suitable for the collection of aliphatic ketones, and activated coconut carbons are not suitable for cyclohexanone.