Quantile spectrum visualization of BUFFER1 and BUFFER2 datasets. Quantile spectrum visualizations for all 183/114 spectra from BUFFER1/BUFFER2 datasets respectively. The middle, upper, and lower spectra are the 50% (median), 75%, and 25% quantile spectra respectively, calculated pointwise for each mass point. The results show that different machine settings give rise to different statistical behavior of the intensity values registered at the detector. Preprocessing techniques should be able to adapt to this varying behavior.