Matrix Spikes—What Are They?
Regan McMorris, Senior Scientist
You may have seen them on a laboratory report, or perhaps you’ve been asked to collect “matrix spike” samples in the field, but what exactly are these quality control samples?
Analytical instruments are calibrated using a known quantity of the chemical of interest in a standard solution—often reagent water, a suitable solvent, or purified air. However, samples sent to the laboratory sometimes involve a much different “matrix”—such as wastewater, soil, plant or animal tissue, construction materials, or consumer products. To verify that the physical properties or characteristics of the matrix do not interfere with the analytical result, a known concentration of the chemical of interest is mixed into a sample of the required matrix—which is referred to as a matrix spike. The matrix spike is then prepared and analyzed according to the analytical method, and results are compared with an analysis of the parent sample (the original sample with no added spike). If there is no matrix interference, the result of the matrix spike should be equivalent to the result of the parent sample plus the amount of chemical added to the matrix spike sample:
% Recover = |
Matrix spike sample result (ug/L) - Parent (unspiked) sample result (ug/L) Spike Amount (ug/L) |
x 100 |
Matrix spikes measure the analytical methodology’s performance on a specific matrix type. Therefore, including matrix spikes with each different sample matrix type in your research can be valuable. Generally speaking, for environmental samples, the recovery of a matrix spike should be within 75 to 125 percent. However, there are plenty of factors that contribute to high or low recovery, many of which are beyond the control of the laboratory.
As always, the staff at ASL is available to answer all of your QA/QC questions and make recommendations. For more information, on these and other ASL laboratory capabilities, please contact Senior Scientist Regan McMorris at +1.541.768.3119.