A New Approach to High Sensitivity Liquid Chromatography-Mass Spectrometry of Peptides using Nanoflow Solvent Assisted Inlet Ionization

Abstract

Liquid chromatography (LC) solvent assisted inlet ionization (SAII) mass spectrometry (MS) was previously reported to give good chromatographic resolution and MS detection injecting 66ng of a BSA tryptic digest. In analogy to nano-electrospray ionization (nESI), we extend SAII LC/MS to nano-SAII (nSAII) operating at nLmin(-1) flow rates and demonstrate good quality ion chromatograms and mass spectra from injection of as little as 0.7ng of BSA digest onto a capillary LC column. Data dependent fragmentation is demonstrated for injection of 7ng of a BSA digest. This method has advantages over nESI in ease of use and low cost as it requires no voltage and is operational without the necessity of connectors or fragile nESI emitters, although similar constricted tips can be helpful in nSAII to stabilize the signal at low nanoliter flow. At a flow rate of 0.8μLmin(-1), the only requirement for nSAII is that the exit-end of the capillary LC column be adjusted near the aperture of the heated inlet of the mass spectrometer.