= Mass spectrometry matrix effect
A \b[mass spectrometry matrix effect] is a change in an <analyte>'s measured response caused by other constituents of the sample. <Ion suppression> is reduced response; enhanced response is also possible. Here \i[matrix] means the surrounding sample constituents, not a mathematical array or necessarily the deliberately added <MALDI matrix>. Chemical amount, recovery during preparation and ion-source response are distinct contributors to the final signal.
A 2003 study used validation experiments to distinguish matrix effects from recovery and compared ion-spray and heated-nebulizer interfaces under matched sample preparation and chromatography. Its contrast between absolute and relative matrix effects also highlights variation among sample sources.<Strategies for the assessment of matrix effect in quantitative bioanalytical methods based on HPLC-MS MS by B. K. Matuszewski and others>[Abstract, matrix/recovery distinction and interface comparison.]{ref} A response measured in one sample composition is not automatically transferable to every other composition.
For equal analyte amounts and matched acquisition, define a <mass spectrometry matrix factor> as the response in a prepared blank matrix spiked after preparation divided by the response in a neat reference. Values below one indicate suppression in that comparison; values above one indicate enhancement. These ratios describe relative response, not an absolute probability that a molecule becomes a detected ion.
An invented <internal standard> example shows both compensation and its limit. In neat solution, analyte and standard give signals $100$ and $50$, with ratio $2$. In matrix, signals $60$ and $30$ retain ratio $2$: their common $0.6$ response multiplier cancels. If the analyte still gives $60$ but the standard gives $45$, the ratio is $4/3$, only $2/3$ of the neat ratio. The normalized matrix factor is $0.6/0.9=2/3$; merely including an <internal standard> did not ensure matched behavior.
The example assumes the same amounts, linear response and appropriate blank correction. A test for recovery places the analyte before preparation and asks a different question. Likewise, <detector signal clipping> is a later recording failure and need not be caused by sample-matrix chemistry. Identifying the affected stage makes a correction scientifically interpretable.
Back to article page
