Influence of fibre coating in headspace solid-phase microextraction-gas chromatographic analysis of aromatic and medicinal plants

Solid-phase microextraction (SPME) is a solvent-free technique, which is we ll established in headspace analysis since it is sensitive, because of the concentration factor achieved by the fibres, and selective, because of diff erent coating materials which can be used. The performance of eight commerc ially available SPME fibres was compared to evaluate the recoveries of some characteristic components with different polarities and structures present in the headspace of four aromatic and medicinal plants: rosemary (Rosmarin us officinalis L.), sage (Salvia officinalis L.), thyme (Thymus vulgaris L. ) and valerian (Valeriana officinalis L.). The relative concentration capac ity of each fibre on the same components of each plant was also determined by comparing their abundance with that obtained by classical static-headspa ce GC. The partition coefficient, K-1, between the headspace gaseous phase and SPME polymeric coating, and the relative concentration factors, of some of the characteristic components of the plant investigated dissolved in di butyl phtalate, were also determined, under rigorously standardised analysi s conditions. The results showed that the most effective fibres were those consisting of two components, i.e., a liquid phase (polydimethyisiloxane) a nd a porous solid (carboxen or divinylbenzene, or both). (C) 2000 Elsevier Science B.V. All rights reserved.