What does 'carryover' mean in QC contexts?

What does 'carryover' mean in QC contexts?

• A. Data entry error.
• B. Instrument drift.
• C. Residual analyte from a previous sample affecting a subsequent run.
• D. Incorrect specimen labeling.

Answer: (C)

Carryover in QC means that traces of an analyte from a previous sample linger in the analytical system and appear in the next run, causing a residual signal. This happens when residues cling to surfaces such as the injection needle, sample loop, autosampler components, tubing, or the chromatography column and detector. The result is a falsely elevated or skewed reading in the subsequent sample, especially noticeable after analyzing a high-concentration sample followed by a low-concentration one. Detecting carryover often involves running a blank or very low‑level sample after a high‑concentration one to see if the signal persists beyond the expected baseline; if it does, carryover is present. To minimize carryover, implement thorough washing steps between samples, use appropriate wash solvents, optimize injection and loop cleaning, the order of sample runs, and include blanks to monitor for contamination. Choices that describe data entry errors, instrument drift, or incorrect specimen labeling don’t capture this contaminating effect between samples. Data entry errors affect results through recording mistakes, drift is a gradual change in response over time, and labeling mistakes concern sample identity, not carryover between samples.

Carryover in QC means that traces of an analyte from a previous sample linger in the analytical system and appear in the next run, causing a residual signal. This happens when residues cling to surfaces such as the injection needle, sample loop, autosampler components, tubing, or the chromatography column and detector. The result is a falsely elevated or skewed reading in the subsequent sample, especially noticeable after analyzing a high-concentration sample followed by a low-concentration one. Detecting carryover often involves running a blank or very low‑level sample after a high‑concentration one to see if the signal persists beyond the expected baseline; if it does, carryover is present. To minimize carryover, implement thorough washing steps between samples, use appropriate wash solvents, optimize injection and loop cleaning, the order of sample runs, and include blanks to monitor for contamination.

Choices that describe data entry errors, instrument drift, or incorrect specimen labeling don’t capture this contaminating effect between samples. Data entry errors affect results through recording mistakes, drift is a gradual change in response over time, and labeling mistakes concern sample identity, not carryover between samples.