What is a Matrix Spike?

• A. A blank sample.
• B. A production sample labeled QA.
• C. A reference sample.
• D. A QA sample to which one or more measured aliquots of parameters are added to it, taken through all steps; used to assess matrix interference.

Answer: (D)

A matrix spike is a QA sample used to test how the sample’s own components affect the measurement of an analyte. It involves adding a known amount of the analyte to the sample before you go through all the analytical steps, then processing and measuring it just like the real samples. By comparing the measured amount to what was added, you can see how much the matrix (the other substances in the sample) is causing recovery losses or signal interference. If the recovered amount matches the added amount, the matrix isn’t interfering; if it deviates, you’ve got matrix effects to account for.

So the described option matches this idea: a QA sample to which one or more measured aliquots of parameters are added, taken through all steps; used to assess matrix interference. A blank would not test the matrix effect because it lacks analyte; a production sample labeled QA and a reference sample don’t specifically test how the matrix influences recovery through the full method.