Picoelectrospray ionization mass spectrometry using narrow-bore chemically etched emitters

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Chemical Engineering

Background:

• Electrospray ionization mass spectrometry (ESI-MS) typically operates at higher flow rates.
• Reproducible fabrication of emitters for low flow rates (<10 nL/min) has been a significant challenge.

Purpose of the Study:

• To demonstrate stable electrospray ionization at ultra-low flow rates using novel emitters.
• To investigate the impact of low flow rates on mass spectrometry signal response and ion utilization efficiency.

Main Methods:

• Fabrication of narrow orifice chemically etched emitters.
• Operation of electrospray ionization at flow rates as low as 400 pL/min.
• Analysis of peptide samples at varying concentrations and flow rates.

Main Results:

• Stable electrospray achieved at flow rates down to 400 pL/min.
• Observed concentration-dependent MS signal response: optimum at ~1 nL/min (low concentration), monotonic decrease at higher concentrations.
• Demonstrated high signal-to-noise ratios for trace amounts (500 zmol) of peptides.
• Ion utilization efficiency increased exponentially with decreasing flow rate.
• Analyte-dependent ionization efficiency noted for peptide mixtures.

Conclusions:

• Ultra-low flow rate ESI-MS with chemically etched emitters is feasible and beneficial.
• Low flow rates significantly improve ion utilization efficiency, crucial for mass-limited samples.
• This approach is highly promising for the analysis of trace biological samples and minimizing sample dilution.