Type of quality-control sample used to evaluate the effects of sample matrices on the performance of an analytical method

• A. Matrix Duplicate
• B. Matrix Spike
• C. Method Blank
• D. Reagent Blank

Answer: (B)

The concept being tested is how the sample matrix affects an analytical method’s performance by checking recovery with a known amount of analyte added to that matrix. A matrix spike involves adding a precise amount of the target analyte to the actual sample matrix and processing it through the same method used for unknowns. By comparing the measured amount to what was added, you see how much the matrix interferes with extraction, detection, or quantitation—revealing matrix effects like suppression or enhancement and overall accuracy. If recovery is near the added amount, the matrix isn’t significantly affecting the method; if recovery is off, the matrix is altering the result and needs consideration in interpretation or method adjustment.

The other options don’t probe this matrix-related performance in the same way: a matrix duplicate is simply a second portion of the same matrix used to assess precision and reproducibility, not recovery or matrix effects; a method blank checks for contamination or background signals introduced by the analytic process itself; a reagent blank checks for contaminants in the reagents used.