posted on 2024-01-03, 21:29authored byChi-Feng Tu, Yu-Chie Chen
In
ambient ionization mass spectrometry (MS), a customized metal
inlet is typically adapted to the orifice of the mass spectrometer
for ease of introduction of the sample. We herein explore that the
metal inlet coiled with a copper wire (∼50 μm) can be
directly used as an ion source to induce corona discharge-like processes
for ionization of analytes in the gas phase. When the metal inlet
is subjected to a high voltage in the mass spectrometer, the electric
field provided by the mass spectrometer enables the generation of
corona discharge to ionize volatile/semivolatile analytes derived
from the sample in the condensed phase. The limit of detection for
azulene derived from the aqueous sample was as low as ∼1 pM.
Moreover, we also demonstrated the feasibility of coupling ultraviolet–visible
absorption spectroscopy with MS by using the metal inlet coiled with
a thin copper wire as the interface. Integration of these two techniques
enables the simultaneous acquisition of spectra from both instruments
for quantitative and qualitative analysis of the sample. Furthermore,
we showed that polar and nonpolar analytes in a mixture can be acquired
in the same mass spectrum by simply depositing a sample droplet (∼20
μL) on a dielectric substrate near the copper wire-coiled metal
inlet of the mass spectrometer. The ionization processes involved
both electrospray ionization and corona discharge. To demonstrate
the applicability of our method for detecting nonpolar and polar analytes
in complex samples, we spiked a nonpolar analyte, benzo[a]pyrene, to a spice sample and successfully detected analytes with
different polarities using our approach.