Headspace solid-phase microextraction (HS-SPME): a microscale sampling technique for determination of monoterpene hydrocarbons in coniferous needles by gas chromatography/mass spectrometry (GC/MS)

Abstract

A headspace solid-phase microextraction (HS-SPME) technique has been applied for the microscale sampling (single needle for Picea omorica, two needles of Picea abies) of volatile monoterpene hydrocarbons (MTHs) from conifer needles. A simple device consisting of a closed headspace vial equipped with an integral cutting device was used for the collection, homogenisation, and HS-SPME sampling. The highly sensitive gas chromatographic/mass spectrometric (GC/MS) analyses (LODs in tenths of ng g(-1) FW were obtained for 3xS/N criteria) of individual needles confirmed the space distribution of MTHs in different parts of a single sprout (base, centre, apex) and among the left, central and right sprout of a whorl. The highest concentrations of MTHs were found in the apical (leading) sprout (S) of a whorl. The serious increase of MTHs content near the base of the left (SNL) sprout and nearly zero concentrations in the central parts of both the side sprouts of P. abies corresponded to the morphology of the whorl. On the other hand, similar concentrations of MTHs were found in the apex of the side (SNL and SNR) sprouts. The distributions of MTHs obtained after HS-SPME and solvent extraction followed the similar trends for both species. HS-SPME is more suitable for the evaluation of distribution of volatiles in microscale experiments due to the more precise separation of needles into correct categories and elimination of "averaging" effects of the larger quantities of needles needed for the solvent extraction. The precision was improved by one order of magnitude due to the reduction of uncontrolled losses of volatile species during the sample treatment.