The sum ion abundances (counts⋅s−1) of representative ions and TIC values from rat liver sections were monitored over time. Data points within two vertical gridlines are from the same section. Top: m/z 369.3517, 435.3329, 744.5547, 792.5551, 810.6016 in positive mode; Bottom: m/z 279.2330, 303.2330, 306.0766, 329.2487, 379.0829 in negative mode. Solid brown and blue lines are Lowess smoothed lines fitted to the data points.