The identification of unknown compounds remains to be a bottleneck of mass spectrometry
(MS)-based metabolomics screening experiments. Here, we present a novel approach which
facilitates the identification and quantification of analytes containing aldehyde
and ketone groups in biological samples by adding chemical information to MS data.
Our strategy is based on rapid autosampler-in-needle-derivatization with p-toluenesulfonylhydrazine
(TSH). The resulting TSH-hydrazones are separated by ultrahigh-performance liquid
chromatography (UHPLC) and detected by electrospray ionization-quadrupole-time-of-flight
(ESI-QqTOF) mass spectrometry using a SWATH (Sequential Window Acquisition of all
Theoretical Fragment-Ion Spectra) data-independent high-resolution mass spectrometry
(HR-MS) approach. Derivatization makes small, poorly ionizable or retained analytes
amenable to reversed phase chromatography and electrospray ionization in both polarities.
Negatively charged TSH-hydrazone ions furthermore show a simple and predictable fragmentation
pattern upon collision induced dissociation, which enables the chemo-selective screening
for unknown aldehydes and ketones via a signature fragment ion (m/z 155.0172). By
means of SWATH, targeted and nontargeted application scenarios of the suggested derivatization
route are enabled in the frame of a single UHPLC-ESI-QqTOF-HR-MS workflow. The method's
ability to simultaneously quantify and identify molecules containing aldehyde and
ketone groups is demonstrated using 61 target analytes from various compound classes
and a (13)C labeled yeast matrix. The identification of unknowns in biological samples
is detailed using the example of indole-3-acetaldehyde.