Which of the following best describes the purpose of a matrix spike test in QA/QC?

• A. It assesses long-term instrument calibration stability.
• B. It evaluates the effect of adding a spike on the chromatography peak shape.
• C. It checks if the spike is detected by the instrument.
• D. It adds a known amount of analyte to a sample to evaluate recovery in the matrix and assess method accuracy.

Answer: (D)

Matrix spike testing checks how well a method recovers analyte when it’s present in the actual sample matrix. By adding a known quantity of the analyte to the sample and running it through the full analytical process, you measure how much of that added amount the method can retrieve. This recovery value reveals both method accuracy and any matrix effects that could cause under- or over-recovery, guiding you on whether the method is performing correctly for that specific sample type.

It’s not about the instrument’s long-term calibration stability, which concerns drift over time. It’s not primarily about changes in chromatography peak shape, which would point to separation or injection issues. And it isn’t just about whether the spike is detected at all; the key goal is to quantify recovery and overall accuracy in the presence of the sample matrix.