Fig. 2From: Comprehensive metabolic profiling of Parkinson’s disease by liquid chromatography-mass spectrometryOverview of the detection and identification of metabolites in three cohorts. Briefly, each plasma sample was analyzed by both LC-MS ESI+ mode and ESI- mode to facilitate the ionization and detection of alkaline compounds and acidic compounds, respectively. After peak detection and alignment and metabolite recognition, 226, 202 and 204 metabolites were identified in each cohortBack to article page