Nanospray mass spectrometry with indirect conductive graphite coating

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Separation Science

Background:

• Nanospray mass spectrometry (nESI-MS) requires robust conductive coatings for emitters.
• Existing methods can be costly or lack durability.
• Capillary electrophoresis (CE) coupled with nESI-MS demands sensitive detection.

Purpose of the Study:

• To develop an easy and cost-effective method for manufacturing a robust conductive graphite coating for nESI-MS and CE-nESI-MS.
• To evaluate the stability, solvent resistance, and performance of the developed coating.
• To demonstrate the applicability of the technique for detecting analytes at low concentrations.

Main Methods:

• A graphite coating was applied to a tube sleeve using pencil graphite and epoxy glue, into which the nESI emitter is inserted.
• The coating's stability and solvent resistance were tested over extended use (>80 h).
• Stable electrospray was achieved across a flow range of 150-900 nL/min, and analytes were detected using continuous pumping and CE-nESI-MS.

Main Results:

• The graphite coating demonstrated excellent stability and solvent resistance.
• Stable electrospray was achieved, enabling detection of salbutamol, diphenhydramine, and nortriptyline in the nanomole per liter range.
• Capillary electrophoresis-nESI-MS analysis yielded excellent signal-to-noise ratios for 100-fmol injections.

Conclusions:

• The developed graphite coating method is easy, cost-effective, and robust for nESI-MS applications.
• The technique offers a simple way to exchange nESI emitters and minimizes corona discharge risk.
• This method enhances sensitivity and stability for CE-nESI-MS analyses, making it suitable for detecting trace analytes.