Abstract
Retention indices of monoterpene hydrocarbons were measured at 100°C on a 75m×0.25mm i.d. glass wall-coated open tubular (WCOT) column with polyethylene glycol 20M as a polar stationary phase and on a 45m×0.25mm i.d. stainless steel WCOT column with Apiezon L as a nonpolar one. The difference between the retention indices on these phases (ΔI) was discussed from the point of view of the relation to the molecular structure. The values of ΔI of monocyclic terpene hydrocarbons were found to be predictable by using two kinds of increments, i.e., increments due to double bonds, which are determined separately based on their positions in a molecule, and positional increments, which are determined based on positional relationships between two double bonds and between a double bond and a methyl or isopropyl group. The values of these increments were determined by the least-squares method from the data for C6 and C7 hydrocarbons with a six-membered ring and some monoterpene hydrocarbons. The calculated ΔI values for most hydrocarbons agreed with the observed values within ±5 index units. The possible molecular structures for a observed ΔI value can be estimated by comparison with the calculated values. It was tried to identify pyrolysis products from carvone semicarbazone by using ΔI values, whose mass spectra were similar to one another.
