Ion source and mass spectrometer instrument using the same

Abstract

An ion source includes a body having a gas passage and an orifice. A capillary is inserted into the gas passage so that a tip portion of the capillary extends into the orifice. A gas supplier supplies a gas into the gas passage to form a gas flow through the gas passage along the capillary and through the orifice past a tip of the capillary so that the gas flow sprays a sample solution flowing through the capillary from the tip of the capillary. A flow controller regulates a pressure of the gas in the gas passage to adjust a characteristic value F/S to a predetermined value, where F is a flow rate of the gas flow at standard conditions (20.degree. C., 1 atmosphere), and S is a difference between a cross section of the orifice and a cross section of the tip portion of the capillary in the orifice.

1 . A mass spectrometer comprising:
 a body having a gas passage defined therein, a gas inlet connected to the gas passage and an orifice defined in the body and connected to the gas passage;   a capillary through which a sample solution flows towards a tip of the capillary, at least a portion of the capillary being inserted into the body so that at least a portion of the capillary is surrounded by at least a portion of the gas passage, and so that a tip portion of the capillary including the end of the capillary extends at least partially into the orifice,   a gas supplier, connected to the gas inlet, which supplies a gas through the gas inlet into the gas passage to form a gas flow through the gas passage along the capillary and through the orifice past the tip of the capillary so that the gas flow sprays the sample solution from the tip of the capillary;   a flow controller which regulates a pressure of the gas in the gas passage to adjust a characteristic value F/S to a range between 350 meters/second and 700 meters/second, where F is a flow rate of the gas flow at standard conditions (20° C., 1 atmosphere), and S is a difference between a cross section of the orifice defined in the body having a minimum diameter near the tip portion of the capillary and a cross section of the tip portion of the capillary in the orifice,   wherein S=π(D 2 -d 2 )/4,   wherein D is an internal diameter of said orifice and d is an external diameter of the tip portion of the capillary in the orifice;   a sample solution supplier, connected to the capillary, which supplies the sample solution to the capillary; and   an analyzer which receives gaseous ions formed from the sample solution sprayed by the gas flow from the tip of the capillary, and which analyzes a mass of the gaseous ions,   wherein an axial thickness of a portion of the orifice defined in the body having a minimum diameter near the tip portion of the capillary is not greater than 2 mm, and   wherein the flow controller regulates a pressure of the gas in the gas passage to be 7 atmosphere or less.