UPLC-MS-Based Analysis of Human Plasma for Metabonomics Using Solvent Precipitation or Solid Phase Extraction

A study of the factors involved in obtaining valid global metabolite profiles from the LC-MS of human plasma for the purposes of metabonomic analysis has been undertaken. Plasma proteins were either precipitated with 3 vol of organic solvent (methanol or acetonitrile) or subjected to solid phase extraction (SPE) on a C18-bonded phase. For chromatography, a reversed-phase gradient system, based on acidified water/methanol, was used. Ultra performance liquid chromatography (UPLC) was performed on a C18-bonded stationary phase using sub 2 mu m particles packed into a 2.1 x 100 mm column. The eluent from the column was subjected to analysis by positive electrospray ionization using a time-of-flight mass spectrometer. To obtain reproducible results for solvent-precipitated plasma, the conditioning of the system with injections of matrix prior to the main analytical run was essential. The repeatability of the methodology was improved significantly when the sample preparation was performed using solid phase extraction.