11. ESI Soft ionisation technique; little fragmentation Large molecules may be protonated more than once Peaks seen for same compound with different m/z ratios
45. Adducts and Clusters Formed in LC-MS Cluster/Adduct Source of Cluster Occurence Mass of Cluster Ion [M + CH3COO]- Acetic Acid APCI & IS -ve mode M + 59 [M + Cl]- Chlorinated Solvent APCI & IS -ve mode M + 35 [M + NH4]+ Ammonia APCI & IS +ve mode M + 18 [M + Na]+ Sodium Salts APCI & IS +ve mode M + 23 [M+K]+ Potassium Salts APCI & IS +ve mode M + 39 [M + CH3CNH]+ Acetonitrile APCI & IS +ve mode M + 42 [M+CH3OHH]+ Methanol APCI & IS +ve mode M + 33 [M+H3O]+ Water APCI & IS +ve mode M + 19