For the LOD comparison, full scan mode from 62 to 900 Da at a resolution of 120´000 was used. Data was acquired for both positive and negative polarities, separately. Additional MS parameters are listed in Table . A total of 10 technical replicates were acquired in each polarity at three concentration levels over the linear range: low, medium, and high, corresponding to levels 3, 5, and 7, respectively in Table .