  The aerosols present in the atmosphere of the Saturn s moon Titan are of
particular planetary science interest and several spacecraft missions already
allowed to gather spectroscopic data. Titan haze s analogs, so-called tholins,
were produced on earth to push forward the comprehension of their formation and
properties. In this study, this highly complex mixture was analyzed here for
the first time by trapped ion mobility spectrometry coupled to ultra-high
resolution mass spectrometry (FTICR MS). Electrospray ionization revealed the
characteristic CHNx-class components, with CHN5-6 and DBE 6-7 most abundant.
Deploying specialized visualization, enabled by accurate mass measurements and
elemental composition assignments, the adapted Kendrick mass defect analysis
highlights the C2H3N homolog series, whereas the nitrogen-modified van Krevelen
diagram exhibits a clear trend towards H/C 1.5 and N/C 0.5. More interestingly,
the representation of m/z versus collision cross section (CCS) allowed
hypothesizing a ramified N-PAH structural motif. State-of-the-art IMS is
currently not able to resolve the isomeric continuum of ultra-complex mixtures;
thus peak parameter other than the CCS-value are explored. As such, analyzing
the mobility peak width versus m/z shows a linear increase in isomeric
diversity between m/z 170 and 350 and a near plateau in diversity at higher m/z
for the N-PAH-like structure. Due to the high complexity of the sample, these
structural insights are only to be revealed by TIMS-FTICR MS.
