Table 1 Imaging mass spectrometry ionization techniques: application, advantages, and disadvantages [8, 9, 11].
| Application | Ionization | Advantages | Disadvantages |
|---|---|---|---|
| Tissue molecular imaging | MALDI |
• Label-free analysis • High-sensitivity • Use over a broad mass range • High-spatial resolution (≤ 1 μm) • Application on both formalin-fixed paraffin-embedded (FFPE) tissue microarrays and on fresh tissue samples. |
• Low throughput • Sample preparation can lead to spatial dislocation or chemical modifications • Matrix dependent analysis |
| DESI |
• Label-free analysis • Ambient ionization method • Direct solid surface sampling • Multiple charged ions • Minimal sample preparation • Soft ionization method • Generally less costly upon comparison to MALDI |
• Imaging in the low-mass region—limited use for proteins • Poorer spatial resolution compared to MALDI • Solvent dependent |