posted on 2020-03-10, 11:45authored byValentina Calabrese, Hélène Lavanant, Frédéric Rosu, Valérie Gabelica, Carlos Afonso
In
the last years, ion mobility mass spectrometry (IMS-MS) has
improved structural analysis and compound identification by giving
access to the collision cross section (CCS). An increasingly wide
and accurate database of CCS values is now available but often without
assessment of the influence of different instrumental settings on
CCS values. Here, we present 75 CCS values in helium (DTCCSHe) for phosphoric acid cluster anions [(H3PO4)n – zH]z− with charge state (z) up to 4–. The CCS values, noted DTCCSHe, were obtained with a commercial drift tube ion mobility
mass spectrometer, in helium, by applying a classic multifield approach.
Phosphoric acid clusters are fragile structures that allow to evaluate
the effect of different experimental conditions on the retention of
weak bonds and their effect on CCS values. We probed harsh and soft
voltage gradients in the electrospray (ESI) source before the IMS
and two different voltage gradients in the post-IMS region. The variations
in the ion mobility and mass spectra consisted in a change in the
distribution of the cluster anions aggregation numbers (n) and charge states (z), with a higher amount of
multiply charged species for the soft pre-IMS voltage gradient and
a lower proportion of cluster dissociation for soft post-IMS conditions.
However, the CCS values did not change with experimental conditions
for a given cluster, as long as it stays intact from the IMS to the
mass analyzer. The DTCCSHe were found in good
agreement among 3 to 10 replicated values, with a relative standard
deviation between 0.1 and 1.7%.