Sample Preparation in Centrifugal Microfluidic Discs for Human Serum Metabolite Analysis by Surface Assisted Laser Desorption/Ionization Mass Spectrometry

We introduce a centrifugal microfluidic disc that accepts a small volume in (∼5 μL), performs sample cleanup on human serum samples, and delivers a small volume out, for subsequent metabolite analysis by surface assisted laser desorption/ionization (SALDI) mass spectrometry (MS) or hydrophilic interaction liquid chromatography (HILIC)-MS. The centrifugal microfluidic disc improves the MS results by removing proteins and lipids from serum. In the case of SALDI-MS, sample background electrolytes are segregated from analytes during the spotting process by the action of the SALDI-chip during drying, for further cleanup, while HILIC separates the salts in HILIC-MS. The resulting mass spectra of disc-prepared samples show a clean background and high signal-to-noise ratio for metabolite peaks. Several representative ionic metabolites from human serum samples were successfully quantified. The performances of the sample preparation disc for SALDI-MS and HILIC-MS were assessed and were comparable. Reproducibility, sample bias, and detection limits for SALDI-MS compared well to ultrafiltration sample preparation.