Overview
Capillary electrophoresis (CE) capillaries contain extremely small internal diameters, making them susceptible to blockage by microscopic particles. Even very small amounts of particulate contamination from buffers, samples, or water can obstruct flow and negatively impact system performance.
One of the most common indicators of a capillary blockage is an unexpected decrease in operating current.
Recognizing the Symptoms of a Blocked Capillary
A partial or complete blockage may result in:
- Sudden loss of current
- Reduced electroosmotic flow
- Poor migration reproducibility
- Inconsistent peak performance
- Complete loss of separation performance
Because CE capillaries have very small internal diameters, particles that would be insignificant in other analytical techniques can create significant flow restrictions.
Recommended Recovery Procedure
When a blockage is suspected, flushing the capillary may help remove the obstruction.
Step 1
Obtain freshly filtered, CE-grade deionized water. Using high-purity, particle-free water is important to avoid introducing additional contaminants into the capillary.
Step 2
Connect an appropriate syringe to the capillary.
Step 3
Flush the capillary in the reverse flow direction.
Reverse flushing is recommended because particles frequently become trapped near the inlet end of the capillary. Flushing from the opposite direction can help dislodge and remove the obstruction more effectively.
Step 4
Apply sufficient pressure to encourage removal of the particulate material. Care should be taken to avoid excessive force that could damage the capillary.
Step 5
Verify that normal flow and operating current have been restored before returning the capillary to service.
Preventing Future Blockages
The best solution for capillary blockages is prevention.
Materials introduced into the capillary should be thoroughly filtered prior to use, including:
- Buffers
- Deionized water
- Sample solutions
- Reagents
Proper filtration helps minimize the introduction of particles that can accumulate and restrict flow.
Best Practices for CE Capillary Care
To reduce the likelihood of blockage:
- Use CE-grade reagents whenever possible.
- Filter all buffers before use.
- Filter all sample solutions.
- Use clean laboratory practices.
- Flush capillaries according to instrument recommendations.
- Inspect solutions for visible particulate matter before analysis.
Routine preventative practices can significantly improve capillary lifetime and performance.
Key Takeaways
- Sudden current loss may indicate a capillary blockage.
- Small particles can easily obstruct CE capillaries.
- Reverse-direction flushing is often the most effective recovery approach.
- Use filtered CE-grade deionized water during flushing.
- Proper filtration of buffers, samples, and water helps prevent future blockages.
- Preventative maintenance is critical for reliable CE performance.