Sample preparation for radiocarbon (14C) measurements of carbonyl compounds in the atmosphere: quantifying the biogenic contribution

A method has been developed for the preparation of samples for radiocarbon (14C) measurements of carbonyl compounds in the atmosphere. Sampling on 25 ml 2,4-dinitrophenylhydrazine (DNPH)- coated silica gel cartridges can be carried out with up to 10.000 ℓ of ambient air with no adverse effects on sample integrity. Methods for the selective clean-up of the extracts have been investigated. This is a necessary step in preparing ambient carbonyl samples for a measurement of the radiocarbon (14C) content. The method which gave the best results include extraction of the DNPH cartridge with CH3CN and purification of the carbonyl hydrazones over activated silica gel to remove excess DNPH and non target compounds. This method has been validated with laboratory samples and has been proved to give reliable results The radiocarbon data from the first field experiment showed that ambient air over a semi-rural test site in Ispra, Italy on a late summer day contained mainly five carbonyls (formaldehyde>acetaldehyde>acetone>propanal>butanal) of a mixed biogenic (41–57%) and anthropogenic (43–59%) origin. The method will be used in future monitoring of radiocarbon (14C) on a number of test sites in Europe.