Generating multiply charged protein ions by ultrasonic nebulization/multiple channel-electrospray ionization mass spectrometry

An ultrasonic nebulization/multiple channel electrospray ionization (USN/MC -ES) source, which generates multiply charged peptides and proteins ions, w as developed. The source is an ultrasonic nebulizer that is connected to a multiple channel electrospray ionization source. Aerosols were formed by ul trasonically nebulizing the sample solution. The aerosols were then purged into the central channel of a seven-channel ES source via nitrogen gas. A m ethanol solution that contained 1% trifluroacetic acid was electrosprayed t hrough the outlying six electrosprayers. Detection of multiply charged pept ide and protein ions indicated that electrospray was generated from the cha rged droplet containing analyte. The sample aerosol appeared to fuse with t he charged methanol droplet in the air. Then electrospray ionization of the analyte occurred from the newly formed droplet. The peptide and protein pr epared in deionized water were detected by this USN/MC-ES-MS. By varying th e electrospray solvents, the signals of certain components in the mixture w ere selectively suppressed.