What could cause a loss in sensitivity or absence of peaks?

Please be aware that performance-related issues that cannot be resolved by instrument cleaning are not within biocrates’ responsibility and must be handled by the user or the LC-MS engineer. Based on our experience, however, we are happy to share some suggestions:

• Sample preparation:
  • Make sure the testmix/test sample has been reconstituted or diluted correctly.
  • Make sure there was no air in the pipette tip when transferring sample to another vial.
  • Make sure the testmix/test sample used was not expired.
• Instrumental setup: double-check all method parameters and make sure the analytical column and mobile phases were prepared and installed correctly.
• Connections: check for leaks and retighten all connections.
• Injection needle: the injection needle might not be correctly adjusted or draws air. Adjust positioning or replace the needle.
• Injector: check for leaks or contaminations in the injector valve and rotor seal. Clean or replace the valve.
• Divert valve: set to waste instead of MS. Check setting at valve and in method.
• ESI electrode: leak, contamination, or defective. Reassemble ESI probe, clean with different solvents at high flow rate, or replace ESI needle.
• MS: perform instrument front-end cleaning (Orifice, QJet, quadrupole, ion transfer tube etc.). Tune and calibrate the instrument.