On the Primary Ionization Mechanism(s) in Matrix-Assisted Laser Desorption Ionization

Figure 4

MALDI mass spectra of Insulin obtained by (a) sinapinic acid only, (b) sinapinic acid with 0.1% of formic acid, (c) sinapinic acid with 0.1% of acetic acid, and (d) sinapinic acid with 0.1% of trifluoroacetic acid.

(a)

(b)

(c)

(d)