Detection of Vapour Emissions from Star Anise Seeds and Mint Leaves using the CO2 Laser Photoacoustic Technique

The aim of this work was to establish the feasibility of the detection of the vapours of the star anise and mint essential oils emitted from the uncrushed seeds of star anise (Illicium verum H.) and from the leaves of Japanese mint (Mentha arvensis L.) respectively using a heat pipe type of photoacoustic cell in conjunction with a line tunable waveguide CO2 laser. Infrared photoacoustic stick spectra were obtained with excellent reproducibility and a high signal-to-noise ratio for the vapour emissions in one atmosphere of nitrogen gas over a temperature range from 20°C up to 180°C in the case of anise seeds and from 20°C to 100°C for mint leaves. Significant differences found between the photoacoustic spectra from the vapour emission of seeds and leaves when compared with commercial samples of the related essential oils are discussed.The financial support for travel from the British Council, East Jerusalem to (DL, MA-T) and that from Royal Society of London to (MA-T, KH) are gratefully acknowledged