Which QA sample is used to verify the accuracy of a method using a known concentration added to a controlled matrix?

• A. Matrix Spike.
• B. Laboratory Control Sample (LCS).
• C. Blank Spike.
• D. Method Blank.

Answer: (B)

The idea being tested is using a known amount of analyte added to a controlled, clean matrix to check how accurately the method measures that amount. A Laboratory Control Sample is prepared in the lab by spiking a known concentration into a controlled matrix, so you can directly compare the measured value to the true value and assess accuracy, recovery, and bias. This setup provides a reliable reference point for method performance.

In contrast, a Matrix Spike uses the actual sample’s matrix to evaluate how well the method handles matrix effects, which is about accuracy in a real-world matrix rather than a clean, controlled one. A Blank Spike involves adding a known amount to a blank matrix to look at recovery in the absence of any matrix. A Method Blank checks for contamination by processing a blank sample through the entire method. Thus, the Laboratory Control Sample best matches the description of verifying accuracy with a known concentration in a controlled matrix.