Figure 1: Principles of mass spectrometry. A: Matrix-assisted laser desorption ionization (MALDI) mass spectrometry is illustrated. Matrix loaded samples are ionized and further characterized with mass analyzer and ion detector; B: Electrospray ionization (ESI) mass spectrometry is accomplished by continuously infusing a sample solution into an electric field, generating very fine charged droplets with soft ionization and yields primarily intact molecular species with little or no fragmentation.