What is matrix effect and how is it quantified?

For research use only. Not for use in diagnostic procedures.

Answer

Matrix effect refers to the loss of analyte signal due to the presence of a matrix such as food, urine, plasma or blood. This signal loss can be quantified by comparing it to the signal of the same analyte in a neat solution. In mass spectrometry, the matrix effect is mostly due to matrix components interfering with the ionization of a particular analyte.

When reviewing analyte response in a results table in SCIEX OS software, users ideally would like to see a higher signal (such as peak area or signal to noise) for extracted quality control (QC) samples, as well as a high level of accuracy (ideally 100%). The matrix effect can significantly attenuate signal and negatively impact accuracy, reducing its value from 100%.

To quantify the effect of matrix on signal, matrix matched blank samples (post extraction) should be spiked and the signal compared with that of a neat standard at the same concentration level. For example, when analyzing pesticides in strawberries, to study the effect of the strawberry matrix on the pesticide signal, an appropriate matrix would be an extract of organically grown strawberries. After extracting the organic strawberry, 900 µL of the fruit extract should be spiked with 100 µL of a 50 ppb pesticide spiking solution to make a 5.0 ppb pesticide solution in matrix. For a neat standard, a 100 µL of 50 ppb standard would be added to 900 µL of pure, matching solvent.

Now, if the signal in the matrix solution is 70% of the signal for the neat standard, this means 30% of signal is lost due to matrix effect. In other words, instrumental recovery is 70% due to matrix effect.

Additional information about the matrix effect can be found in these links:
https://sciex.com/support/knowledge-base-articles/why-do-extracted-samples-and-quality-controls-have-lower-signal-compared-to-neat-standards_en_us

https://sciex.com/support/knowledge-base-articles/how-to-reduce-matrix-effect_en_us