What is carryover, and how is it assessed during method validation?

What is carryover, and how is it assessed during method validation?

• A. Carryover is cross-contamination between different solvents.
• B. Carryover is residual analyte from a high-concentration sample contaminating the next injection.
• C. Carryover is the backup of samples in the freezer.
• D. Carryover is cross-lab data sharing.

Answer: (B)

Carryover refers to residual analyte from a high-concentration injection that remains in the system and appears in the next injection. In method validation, this is tested by running a high-concentration sample (a calibrator or QC at the upper end of the range) followed by one or more blank or very low concentration injections. Any signal at the analyte’s retention time in those subsequent injections is measured and expressed as carryover (often as a percentage of the high-concentration response or of the blank/LLOQ response). The goal is to ensure the carryover is below predefined acceptance criteria, so that a high-result sample does not falsely inflate the signal in the next run and lead to erroneous results. If carryover is detected, the method is refined—through additional wash steps, improved autosampler rinsing, column conditioning, or changes to injection sequences—to bring carryover within acceptable limits. This concept is distinct from cross-contamination between solvents, freezer backlogs, or sharing data between labs, which are unrelated issues to how leftover analyte from a previous injection can affect a subsequent measurement.

Carryover refers to residual analyte from a high-concentration injection that remains in the system and appears in the next injection. In method validation, this is tested by running a high-concentration sample (a calibrator or QC at the upper end of the range) followed by one or more blank or very low concentration injections. Any signal at the analyte’s retention time in those subsequent injections is measured and expressed as carryover (often as a percentage of the high-concentration response or of the blank/LLOQ response).

The goal is to ensure the carryover is below predefined acceptance criteria, so that a high-result sample does not falsely inflate the signal in the next run and lead to erroneous results. If carryover is detected, the method is refined—through additional wash steps, improved autosampler rinsing, column conditioning, or changes to injection sequences—to bring carryover within acceptable limits.

This concept is distinct from cross-contamination between solvents, freezer backlogs, or sharing data between labs, which are unrelated issues to how leftover analyte from a previous injection can affect a subsequent measurement.