Depth profiles were acquired from cells that were freeze-dried (FD) and from those that were formaldehyde-fixed (FF). 311 ions were selected that were detected in the spectra of both sample types. The intensity of each ion was summed over the entire depth profile. Intensity values for each ion were averaged and normalized to the total ion dose. For a given ion, the average intensity from the FF cells was divided by the average intensity from the FD cells. The fold difference is plotted on the y-axis as a function of m/z. The red dotted line signifies a (FF/FD) intensity of 1. Error bars signify one standard deviation. All depth profiles were acquired for 1000 seconds, with a 500 μm × 500 μm analysis area and a 700 μm × 700 μm sputter area. For the FD cells, n = 10, from four total samples and three separate data acquisition sessions. For the FF cells, n = 7, from three total samples and three separate data acquisition sessions.