A SONIC SPRAY INTERFACE FOR THE MASS ANALYSIS OF HIGHLY-CHARGED IONS FROM PROTEIN SOLUTIONS AT HIGH-FLOW RATES

We have improved the sonic spray interface to enable the analysis of m ultiply charged ions of protein from a solution at a now rate of 1 mL/ min using a conventional liquid chromatograph/mass spectrometer, in th is interface, we added a multihole plate in front of the sampling orif ice of a mass spectrometer. This plate does not have a hole coaxial to the sampling orifice but has small holes around the central region of the plate. The plate reduces the density of the solvent molecules in the sprayed gas introduced into the vacuum region through the sampling orifice from the atmosphere and prevents the ions from being solvated and becoming charged droplets due to the cooling that follows adiabat ic expansion of the sprayed gas. With this improvement, multiply charg ed ions whose charge distribution ranged from 11+ to 16+ were analyzed from a 1 mu M cytochrome c solution at a high flow rate of 1 mL/min w ithout using a splitter.