Microfabricated
Glow Discharge Plasma (MFGDP) for
Ambient Desorption/Ionization Mass Spectrometry
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Abstract
A novel ambient ionization technique
for mass spectrometry, microfabricated
glow discharge plasma (MFGDP), is reported. This device is made of
a millimeter-sized ceramic cavity with two platinum electrodes positioned
face-to-face. He or Ar plasma can be generated by a direct current
voltage of several hundreds of volts requiring a total power below
4 W. The thermal plume temperature of the He plasma was measured and
found to be between 25 and 80 °C at a normal discharge current.
Gaseous, liquid, creamy, and solid samples with molecular weights
up to 1.5 kDa could be examined in both positive and negative mode,
giving limits of detection (LOD) at or below the fg/mm<sup>2</sup> level. The relative standard deviation (RSD) of manual sampling
ranged from 10% to ∼20%, while correlation coefficients of
the working curve (<i>R</i><sup>2</sup>) are all above 0.98
with the addition of internal standards. The ionization mechanisms
are examed via both optical and mass spectrometry. Due to the low
temperature characteristics of the microplasma, nonthermal momentum
desorption is considered to dominate the desorption process