Which statement about carryover prevention in LC-MS/MS is true?

Which statement about carryover prevention in LC-MS/MS is true?

• A. Thorough autosampler wash
• B. Increasing the solvent flow rate
• C. Shortening the autosampler dwell time
• D. Reducing solvent polarity

Answer: (A)

Carryover in LC-MS/MS happens when analyte from a previous sample sticks to surfaces in the injection path and shows up in the next run. The most effective way to prevent this is a thorough autosampler wash that cleans the needle, injection port, sample loop, and connected lines between injections. By using strong, appropriate wash solvents and often multiple wash cycles, you remove residues that could be carried over into subsequent analyses, reducing false positives or inflated results.

Rationale for the other ideas: simply increasing the solvent flow rate might speed up flushing but can introduce new issues and still may not remove residues that cling to surfaces. Shortening the autosampler dwell time reduces contact time but doesn’t guarantee complete cleaning. Reducing solvent polarity could affect solubility and chromatographic behavior, and it doesn’t address cleaning surfaces. In practice, a thorough autosampler wash (often with multiple cycles and validated solvents) is the most direct and reliable method to minimize carryover between runs.