DECOMPOSITION OF TERPENES BY OZONE DURING SAMPLING ON TENAX

The ozonolytic decomposition of terpenes and terpenoids during samplin g on Tenax is investigated in an artificial air system at ambient conc entration levels, The detrimental effect of 8-150 ppbv ozone depends o n the chemical structure of the compounds: saturated terpenoids such a s 1,8-cineole, camphor, and bornyl acetate are unaffected by ozone, Th e terpenes and terpenoids which containing one C-C double bond are sli ghtly decomposed in the order camphene < beta-pinene approximate to my rtenal < alpha-pinene < sabinene approximate to citronellal. The compo unds containing two or more double bonds are significantly decomposed in the order d-limonene approximate to citral < linalool < beta-ocimen e < terpinolene << alpha-terpinene approximate to beta-caryophyllene. For alpha-pinene, sabinene and d-limonene, their ozonolysis products a re found on the tubes: pinonaldehyde, 5-(1-methylethyl)bicyclo[3.1.0]h exan-2-one, and 3-(1-methylethenyl)-6-oxoheptanal. The analytical reco veries are significantly enhanced for many compounds when the sampling duration is reduced from 10 min to 30 s, explained by the time availa ble for ozonolysis, A miniature ozone scrubber with multiple layers of MnO2-coated copper nets was developed and thoroughly tested, The opti mal number of plies is found to be 8, which ensures quantitative recov eries for all test compounds except alpha-terpinene, beta-caryophyllen e, citral, and citronellal. The results that are reported here call in to question previous data on terpenes and terpenoids and/or their oxid ation products where measurements have been carried out without the pr ior removal of ozone.