Patent ID: 8269165

Claim:
A method for nanoelectrospray ionization, comprising: a first step of introducing a separation solvent comprising a sample and an organic solvent into a column-unified needle filled with a resin for liquid chromatography and spraying a separated sample component into a sample-introducing orifice of a mass spectrometer through a tip portion of the column-unified needle; and a second step of introducing an organic solvent into a solvent-feeding needle and feeding the organic solvent to the tip portion of the column-unified needle through a tip portion of the solvent-feeding needle, wherein a concentration of the organic solvent in the separation solvent is regulated to have a gradient of low to high, and wherein at least in an early stage of the process in which the concentration of the organic solvent in the separation solvent is regulated to have a gradient, the first and second steps of introducings are conducted substantially simultaneously.