Rearrangement ofp-menthane terpenes by Carboxen during HS-SPME

The commercially available 75 μm Carboxen-Polydimethylsiloxane (PDMS) fibre for solid phase microextraction (SPME) has been shown to rearrange some monoterpenoids to p-cymene during headspace (HS)-SPME analysis. Ten commonly encountered monoterpenoids varying in structural and/or functional group were used as test compounds. The p-menthane hydrocarbons α- and γ-terpinene, α-phellandrene, and terpinolene were the only analytes rearranged by the Carboxen-PDMS coating with p-cymene/analyte ratios determined to be higher than those obtained by the 100 μm PDMS-coated fibre used for comparison. The much higher (>10 times) level of moisture adsorbed by the Carboxen-PDMS coating when compared to the PDMS coating is considered to be one of the factors responsible for the rearrangement process.