On-line CE-MS using pressurized liquid junction nanoflow electrospray interface and surface-coated capillaries

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Coupling capillary electrophoresis (CE) with mass spectrometry (MS) is crucial for analyzing complex biological samples.
• Traditional interfaces can be complex, expensive, and require external pumps for stable electrospray ionization (ESI).

Purpose of the Study:

• To develop a simple, cost-effective, and robust laboratory-made liquid junction interface for CE-MS.
• To achieve stable electrospray generation without external pumps for improved CE-MS analysis.

Main Methods:

• A novel liquid junction interface was designed, positioning the CE capillary and spray tip within an electrode vessel containing spray liquid.
• Electrospray potential was applied via an electrode within the liquid junction, enabling stable nanoliter-per-minute flow rates.
• Optimization involved adjusting the distance between the capillary and spray tip, and pressure applied to the liquid junction.

Main Results:

• A stable electrospray was achieved at low flow rates without external pumps, enhancing spray tip durability.
• Independent optimization of CE separation (including coated capillaries) and ESI conditions was demonstrated.
• The system achieved a limit of detection (LOD) below 10 ng/mL for beta-blocker drugs and below 200 ng/mL for peptide analysis.

Conclusions:

• The developed liquid junction interface offers a simple, cost-effective, and efficient solution for CE-MS coupling.
• This approach facilitates robust and sensitive analysis of diverse samples, including drugs, peptides, protein digests, and biological fluids.