Microsphere entrapped emitters for sample preconcentration and electrospray ionization mass spectrometry

Area of Science:

• Analytical Chemistry
• Materials Science
• Nanotechnology

Background:

• Traditional electrospray ionization (ESI) emitters face challenges with clogging and dead volume.
• Developing robust and efficient emitters is crucial for sensitive mass spectrometry (MS) analysis.

Purpose of the Study:

• To construct and characterize a novel nano-electrospray emitter using entrapped octadecylsilane (ODS) particles.
• To evaluate the performance of the emitter for stable electrospray generation and sample preparation.

Main Methods:

• Fabrication of a nano-electrospray emitter by entrapping ODS microspheres in a photoinitiated polymer at a capillary exit.
• Testing emitter stability under high pressure (>4000 psi).
• Evaluating electrospray sensitivity and signal stability across various flow rates (100-1000 nL/min).
• Assessing emitter performance for solid-phase extraction (SPE) and preconcentration of peptides prior to MS analysis.

Main Results:

• The hybrid microsphere/polymer material demonstrated high pressure resistance.
• 3-micrometer ODS microspheres yielded the most sensitive and stable electrospray between 100-1000 nL/min.
• Low variance (8%) in total ion current (TIC) was observed across multiple emitters.
• Successful solid-phase extraction and preconcentration of leucine enkephalin peptide (20-700 fmol) were achieved.

Conclusions:

• The novel entrapped ODS microsphere emitter design effectively minimizes clogging and dead volume.
• This emitter provides sensitive and stable electrospray ionization for MS applications.
• The integrated emitter design is suitable for both direct infusion and on-emitter sample preparation, enhancing analytical workflows.