Figure 23. Comparison of pyrolysis mass spectra of Douglas fir wood obtained on different instruments: (a) Automated Py-MS apparatus; F.O.M. Institute, Amsterdam; (b) Extranuclear Labs. Py-MS instrument, Biomaterials Profiling Center, University of Utah. Difference in peak intensities in the low mass range of the spectra probably represent residual solvents (water, methanol) and/or different ion transmissivities of the quadrupole filters. Conditions: sample 10 yg; Tc 510°C; Eel (a) 14 eV and (b) 11 eV.

indication of the actual electron and ion energies involved. The spectra in Figures 23 and 24 were obtained with minimal effort to obtain optimum correspondence between the systems and thus do not represent the ultimate degree of inter-laboratory reproducibility obtainable.

Since differences in relative ion transmission are a widely recognized problem in quadrupole instruments, magnetic instruments would appear to offer considerable advantages with regard to inter-laboratory reproducibility in Py-MS. Inherent disadvantages, however, such as slower scanning rates, lower sensitivity in low and medium mass ranges and higher vulnerability to ion source contamination problems,

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