Figure 2.

(A) Extracted ion chromatogram for the [M + 4H]⁴⁺ charge state of glucagon (and the corresponding ¹³C isotope cluster) from the 30‐min analysis of Case study 2. Glucagon has a retention time of 15.87 min. (B) Manual annotation of glucagon MS/MS spectrum, showing multiple b‐ion fragments from the [M + 4H]⁴⁺ charge state of m/z 871.6. The precursor m/z of 871.6 was selected to allow more glucagon ¹³C isotopes into the mass spectrometer for fragmentation to boost signal [Color figure can be viewed at http://wileyonlinelibrary.com]