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. Author manuscript; available in PMC: 2019 Jan 1.
Published in final edited form as: Biotechnol Bioeng. 2018 Nov 6;116(1):121–131. doi: 10.1002/bit.26832

FIGURE 4.

FIGURE 4

Resulting mass spectra from direct infusion electrospray ionization mass spectrometry (ESI-MS) through the dynamic mass spectrometry probe (DMSP) of a solution with 100 mM KCl and 5 μM cytochrome-c. A, Untreated, that is, empty conditioning channel—no characteristic cytochrome-c peaks are visible due to salt interference; B, 1% acetic acid (AA) reveals a strong cytochrome-c signal; C, Addition of ammonium acetate improves intensity of signal; D, Addition of 2% 3-nitrobenzyl alcohol (m-NBA) shifts to a higher charge state distribution; E, Addition of 50% methanol also increases the average charge state, but long-term operation is hindered due to increased inorganic salt precipitation, which can result in clogging of the device [Color figure can be viewed at wileyonlinelibrary.com]