Abstract Matrix spectroscopy is useful as an analytical tool provided certain fundamental modifications are made in experimental technique. Apparatus requirements and sample preparation procedures are detailed. Only conventional spectrometric instrumentation is used. Infrared pseudo matrix isolation (PMI) spectroscopy is shown to be useful for qualitative analysis of complex gas mixtures. The method applies to all volatile infrared absorbing materials. Pseudo matrix isolation has estimable quantitative properties and PMI spectra are readily reduced to tabular form for machine handling. Detection sensitivities of 0.05 μmoles of reagent deposited per square centimeter of substrate are not uncommon. The simplicity of pseudo matrix isolation suggests a variety of applications for matrix spectroscopy relating mainly to the spectra of stable molecules. A whole new time scale for matrix experiments is introduced.