Figure 3.

Mass spectrum obtained from 1 mL of the Kallikrein Inhibitor peptide (Ac-Pro-Phe-Arg-Ser-Val-Gln-NH₂) solution (0.16 nmol/mL), concentrated on the trapping cartridge containing a hydrophilic modified styrene polymer solid phase extraction material (HLB). The cartridge was then washed with water (5 mL, LC/MS grade) to remove contaminants such as saline and was then injected on to the LC/MS system. The protonated molecular ion, [M+H]⁺, is the only peak seen in the mass spectrum.