Ion source and mass spectrometer

An ion source comprising:

• a capillary into which a sample liquid solution is introduced, the capillary being configured to supply an ion or a droplet;
• and
• a pipe configured to supply a sample liquid solution to the capillary, wherein:
• the capillary has a capillary upstream-side end face on an upstream side, and has a capillary downstream-side end face on a downstream side, and an outer diameter of the capillary upstream-side end face is greater than an outer diameter of the capillary downstream-side end face;
• the capillary has a large-diameter part that forms the capillary upstream-side end face on the upstream side, and the large-diameter part has a large-diameter part downstream side face on the downstream side;
• the pipe has a pipe downstream end face on the downstream side;
• the ion source includes a capillary retaining unit configured to retain the capillary, the capillary retaining unit having an upstream end and a downstream end;
• the capillary retaining unit has a hole proximate to the upstream end of the capillary retaining unit through which the capillary downstream-side end face is passable and has a face on which the large-diameter part downstream side face is installable;
• the ion source includes a pipe retaining unit configured to retain the pipe;
• and
• the capillary retaining unit and the pipe retaining unit are disposed such that the capillary upstream-side end face contacts the pipe downstream end face to connect the capillary to the pipe,
• wherein the capillary retaining unit hole comprises a tapered part, the tapered part having a wider diameter at the upstream end of the capillary retaining unit and tapering to a narrower diameter downstream of the upstream end of the capillary retaining unit.