Acetone and perdeuterated acetone in UV-IMS
Ansgar T. Kirk
Received: 2 May 2018 / Revised: 24 May 2018 / Accepted: 25 May 2018
Springer-Verlag GmbH Germany, part of Springer Nature 2018
Measuring a mixture of acetone and perdeuterated acetone (acetone-d6) with an ultra-high resolution drift time ion mobility
spectrometer (resolving power of R
= 235) and ultraviolet ionization (10.6 eV) at ambient pressure reveals three separated peaks.
Two of the peaks can easily be associated with acetone and perdeuterated acetone. In a former publication several findings
indicated an exchange of a methyl group and the formation of a H
related peak. In this work the formed ion species were
analyzed with a high resolution drift time ion mobility time of flight mass spectrometer. The mass spectra clearly show the
formation of three proton-bound dimer peaks whereas the peak between acetone and acetone-d6 is a proton-bound mixed dimer
consisting of one acetone and one acetone-d6 molecule.
Ultra-high resolution IMS
Atmospheric pressure photoionization
The separation of ions in drift time ion mobility spectrometers
(IMS) is based on the collision of the ions with neutral drift
gas under the influence of an electric field . Since IMS are
often operated at ambient pressure (without the need of bulky
vacuum pumps), and have extremely low limits of detection
and even ppt
in less than a second) when operated
with atmospheric pressure chemical ionization (APCI)
sources [2–5], they are widely used in several applications.
Besides the academic value of ultra-high resolution IMS,
e.g. for investigating ion formation processes, ultra-high res-
olution is required in applications where pre-separation is too
time-demanding, e.g. in most security applications [6–9], but
target compounds and interferents have similar ion mobilities
or target compound peaks are masked by the reactant ion
peak. Furthermore, increasing resolution helps improving
SNR and thus detection limits . Besides APCI, photoion-
ization sources at atmospheric pressure (APPI) are also used in
IMS for substances difficult to ionize by APCI, or to reduce
chemical cross sensitivities possible in APCI [11–18].
The ion mobility K can be theoretically estimated from the
ions’ structure and mass [19–21]orbecalculatedfromexper-
imental IMS measurements. Therefore, K is defined as
E Á t
Whereas L is the length of the drift region, E the electric field
in the drift region and t
the drift time of the ions needed to pass
the drift region. Usually, this value is normalized to a temper-
= 273.15 K and a pressure p
= 1013.25 hPa.Theso
called reduced mobility K
¼ K Á
is expected to be nearly
independent of the ambient conditions and instrumental design.
 It can be used to roughly compare peaks between different
IMS instruments. However, this approach does for example not
take into account the drift and sample gas composition (e.g.
water content), the electrical field strengths in the drift region,
and further temperature effects, all affecting the ion mobility.
Thus, several K
values for acetone can be found in literature.
For example, Vautz et al.  reported a value of K
,whereasXieetal. published a value of
both for acetone ions in nitrogen ionized
with a 10.6 eV photo ionization source. Xie et al. assigned the
peak to a protonated acetone monomer, whereas Vautz et al.
only stated the mobility according to the peak position without
further clarification of the ion species.
In Fig. 1 (top), an ultra-high resolution ion mobility spec-
trum (10.6 eV photo ionization source) of a mixture of acetone
* Christian-Robert Raddatz
Institute of Electrical Engineering and Measurement Technology,
Department of Sensors and Measurement Technology, Leibniz
Universität Hannover, Appelstr. 9A, 30167 Hannover, Germany
International Journal for Ion Mobility Spectrometry