The isolation of anylyte molecules in a matrix or on a substrate makes
PDMS-spectra more reproducible and often enhances the detection sensitivity,
especially if the formation of stabile analyte ions is supported by chemical or
other process-induced interactions between analyte and matrix/substrate. These
interactions have a strong influence on the PDMS-yield. The PDMS-yield is also
strongly dependent on analyte-analyte interactions if the analyte concentration
is high. For example, high local concentrations which are produced by
self-aggregation or cluster formation have a considerable effect on the
PDMS-yield. Precise informations about the amount and the formation of
molecules on the sample are required for studying these correlations. We
applied optical spectroscopy methods for characterizing our samples. The
absorption of light from the near IR to UV ( via diffuse reflectance ) and the
fluorescence ( steady state and time-resolved ) were determined. Many
informations about sample composition and structure can be obtained by
evaluating the optical spectra. The determination of low analyte concentrations
is one of the very useful advantages of this application. For example, a
coverage of 6*10^12 adsorbates per cm^2 can be determined precisely enough by
the diffuse reflectance method.