Preparation of Samples for MALDI-TOF/MS Lipid Analyses

A total of 3 μl lipid extract in chloroform solution (10 mg/ml) was diluted in 27 μl of 2-propanol/acetonitrile (60/40, by volume), then 10 μl of the diluted solution were mixed with 10 μl of matrix solution (9-AA, 10 mg/ml in 2-propanol/acetonitrile 60/40, by volume), as previously described (Sun et al., 2008; Angelini et al., 2015). The resulting lipids-matrix solution was then spotted onto the MALDI target (Micro Scout Plate, MSP 96 ground steel target) in droplets of 0.35 μl and analyzed as described above.

After the evaporation of the matrix solvent, the samples are ready to be directly analyzed with MALDI-TOF/MS.