Optimization and Application of Paper-Based Spray Ionization Mass Spectrometry for Analysis of Natural Organic Matter

In
this study, paper-based ionization techniquespaper spray
ionization (PSI) and paper spray chemical ionization (PSCI)were
evaluated and applied for high-resolution mass spectrometry (MS)-based
analysis of natural organic matter (NOM). Methanol:isopropyl alcohol
(50:50, v/v) and ethanol emerged as good spray solvents for PSI, and
hexane:dichloromethane (50:50, v/v) was a good spray solvent for PSCI.
PSI-MS spectra could be obtained with NOM samples on the microgram
scale, which is a critical advantage over conventional electrospray
ionization (ESI)-MS when the amount of available sample is limited.
In addition, PSI is more tolerant to salt contamination than ESI for
NOM analysis. PSCI preferentially ionized less polar compounds, which
may not be ionized well using ESI. Therefore, PSCI can be used as
a complementary method to ESI or PSI. Comparison of the numbers of
peaks obtained with ESI-, PSI-, and PSCI-MS showed that employing
PSI and PSCI can increase the number of compounds that can be detected
by high-resolution MS. In conclusion, the data presented in this study
showed that PSI and PSCI are suitable ionization techniques for NOM
analysis. To the best of our knowledge, this is the first study evaluating
and applying PSI and PSCI for NOM analysis.