Define a matrix spike (MS) and explain its use in QA/QC.

Define a matrix spike (MS) and explain its use in QA/QC.

• A. A matrix spike is a blank sample used to check background contamination.
• B. A matrix spike adds a known amount of analyte to a sample to evaluate recovery in the matrix and assess method accuracy.
• C. A matrix spike is a duplicate of the sample to test precision.
• D. A matrix spike is an instrument calibration standard.

Answer: (B)

A matrix spike tests how well the method works in the actual sample matrix by adding a known amount of analyte to the sample before processing. This lets you see how much of the analyte is recovered through extraction and analysis in that specific matrix, which reveals any matrix effects or biases in the method. By comparing the measured increase to the amount added (often using percent recovery = [measured after spike − native sample level] / amount added × 100), you can judge accuracy and reliability of the results for that matrix. This helps ensure the method performs properly across real samples, not just in clean solvent. This differs from a blank (which checks background contamination without any analyte), a duplicate used to assess precision, or a calibration standard (which sets instrument response).

A matrix spike tests how well the method works in the actual sample matrix by adding a known amount of analyte to the sample before processing. This lets you see how much of the analyte is recovered through extraction and analysis in that specific matrix, which reveals any matrix effects or biases in the method. By comparing the measured increase to the amount added (often using percent recovery = [measured after spike − native sample level] / amount added × 100), you can judge accuracy and reliability of the results for that matrix. This helps ensure the method performs properly across real samples, not just in clean solvent.

This differs from a blank (which checks background contamination without any analyte), a duplicate used to assess precision, or a calibration standard (which sets instrument response).