Anna Wajs*, Andrey Pranovich, Markku Reunanen, Stefan Willför and Bjarne Holmbom

Abstract: Solid-phase microextraction (SPME) combined with GC and GC/MS was used for analysis of the wood volatiles of Norway spruce (Picea abies L.), Scots pine (Pinus sylvestris L.), and European larch (Larix decidua Mill.). More than 160 compounds were extracted and identified from spruce, pine, and larch stemwood. Differences in the quantitative and qualitative composition of the volatiles from the different conifer species were found. The volatile composition was specific for each species. Only small differences in the volatiles from different wood tissues, i.e. sapwood and heartwood, were found.

The volatile extractives in wood tissues of different tree species are unique and may be used for species identification. Terpenes are abundant and diverse in conifers, and play a complex, vital role in the relationship between plants and insects. Signals for sexual reproduction (pheromones, kairmones), for defence against herbivores (allomones), or to attract natural predators of herbivores (synomones) are conveyed through volatile terpenoids (1,2). The role of terpenoids in plants has been frequently discussed in the literature (3,4). There are several methods available for determining terpene composition. A decade ago, a simple, fast, solvent-free sampling technique called solid-phase microextraction (SPME) was introduced (5). This method has been used extensively e.g. in trace analysis of volatiles in environmental samples (6-8). In most cases, SPME sampling has considerable advantages over other commonly used methods, which can be time-consuming or require more complicated techniques and larger amounts of sample. However, the sensitivity of SPME towards external factors (i.e. small differences in vial shape, sampling time, and condition of the fiber) still complicates the use of this method in quantitative analysis (5). Nevertheless, SPME has proved to be a viable alternative method for the determination of volatiles when the amount of sample is limited (8). Previous studies have shown that headspace-SPME (HS-SPME) is a convenient method for determination of volatiles from wood (9,10). Moreover, the headspace analysis (HS-GC) of pine terpenes was more suitable for quantification of highly volatile compounds than the conventional hydrodistillation (11). Thus the headspace-SPME method was now applied to study the volatiles released from wood of Picea abies (Norway spruce), Pinus sylvestris (Scots pine), and Larix decidua (European larch). The aim of the present work was to obtain a better knowledge of wood volatiles of industrially important trees, by analyzing these compounds using HS-SPME which, to our knowledge, has not yet been investigated. Moreover, there is no information about wood volatiles of European larch. Although some studies on the chemical composition of wood volatiles from spruce and pine have been published (3,4,12-18) there is only one publication that has examined pine volatiles with the SPME method, however, in much less detail (9). Nevertheless, several studies on volatiles from different parts, that is needles, bark, and wood of spruce (9,19-21), pine (11,15,22-26) and larch (27,28) have been conducted. This paper deals with the composition of the volatiles released from different wood tissues, i.e. sapwood and heartwood, of Norway spruce, Scots pine and European larch. We compared both the qualitative and quantitative composition of volatiles obtained by HS-SPME and GC analysis.