Fig. 22 The mass spectra obtained with NEDC, norharmane, DAN
and 9AA matrix.
Considering the performance of different matrices in the negative
ionization mode (Fig. 22), norharmane matrix could be rejected since it
has low peaks intensity and, as a result, it losses the information from
the low MW range (e.g., peaks from fatty acids). NEDC is even worse for
low MW peaks, but at least it can provide the ion maps for specific
substances like glucose, n-acetyl-aspartic acid, glucose-6-phosphate,
glucose-3-phosphate, and glutamic acid. DAN matrix produces higher peaks
intensity in a lower mass range and seems to provide more information
than 9AA. Additionally, it provides quite high intensities and
signal-to-noise ratios. So, we recommended NEDC for particular tasks
such as glucose analysis, and DAN for the lipids analysis in negative
ionization mode.
Table 1. Summary of sample preparation optimization with the
aid of wet-interface matrix deposition device (SunCollect®) for MALDI
MSI (L – the number of matrix layers, Z - different spraying nozzle
height).