In annotation process, KEGG, KNApSAcK and LipidMAPS are used for primary database search. Peaks with no hit to these databases are then selected to secondary search using exactMassDB and Pep1000 databases. After the database search processes, each database hits are manually checked to assign a compound name or compound category name. In case of no compound name or compound category name can assign, predicted molecular formulas are used for the annotation. Peaks without predicted molecular formula are assigned as "unidentified" peak.