How is carryover detected in LC-MS/MS runs?

How is carryover detected in LC-MS/MS runs?

• A. Frequent calibration
• B. Blanks after high-concentration samples
• C. Replacing solvent
• D. Lower column temperature

Answer: (B)

Carryover shows up when remnants of a previous injection linger into the next run, producing a signal even though nothing new is present. To detect it in LC-MS/MS, inject a solvent blank right after a high-concentration sample and monitor the same MS transitions as the analyte. If you see a peak in the blank above the noise, that indicates carryover. Testing after a high-concentration injection is crucial because more analyte can adhere to the injector, lines, or column and reveal residual carryover that wouldn’t show up after a low-concentration run.

Frequent calibration checks accuracy but doesn’t reveal residual carryover. Replacing solvent is a mitigation step that can reduce carryover but doesn’t serve as a detection method. Lowering column temperature isn’t a detection approach and can alter retention, not indicator carryover. If carryover is detected, implement wash steps or improved injector/solvent cleanliness and adjust the method to ensure residues are removed between injections.