A NEW APPARATUS FOR LASER MICROPYROLYSIS GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A new instrumental configuration for laser micropyrolysis-gas chromato graphy/mass spectrometric analysis is reported. The principal devices are a high powered continuous wave Nd:YAG laser; a commercial reflecte d light/fluorescence microscope (slightly modified to accommodate lase r radiation), a pyrolysis chamber, a gas inlet system, a gas chromatog raph (modified to accommodate the inlet system) and a hybrid (double f ocusing-quad) mass spectrometer. The mass spectrometer offers very hig h sensitivity (max(m) = 5 x 10(-7) C mu g(-1)) and mass resolution (ma x(m) = 80 000). A Sydney Basin torbanite sample was analysed to test t he efficiency and potency of the instrument. High concentrations of py rolysis products were obtained from the sample with mild laser conditi ons. The dominant products are homologous series of straight chain ali phatic hydrocarbons ranging from C-6 to greater than C-30. Secondary c ontaminant products from sample charring were minimal with laser energ ies in the region of 0.5-3 W, even for continuous exposure of up to 30 0 s duration. To make comparison with more conventional techniques use d for the pyrolysis of organic sediments, the Sydney Basin torbanite s ample was also subjected to gas chromatography/mass spectrometric anal ysis with the following pyrolysis methods: (i) a pyroprobe; (ii) a pyr ojector; and (iii) a quantum microscale sealed vessel (MSSV-1) pyrolys is unit. A comparison reveals similar aliphatic dominated product dist ributions from each pyrolysis method. The consistency of these results proves the capability of the new laser apparatus to perform analytica l pyrolysis at a microscopic level, rather than on bulk samples as req uired by more traditional techniques.