Carryover is when a small part of one injection appears in the next run. It can ruin low-level results.
Common causes
- An inadequate needle wash, or a wash solvent that does not dissolve your sample
- A worn needle seat or rotor seal
- Sample adsorbing onto tubing or fittings
What to try
- Use a stronger wash solvent, and increase wash volume or time.
- Replace worn seals and the needle.
- Run blank injections to find where carryover starts.
- Change the injection order, with low-concentration samples first.
See autosamplers and injectors and HPLC systems.
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