Apparatus and method of preparing reference solution

An apparatus for preparing a reference solution, comprising:

• a gas component detector having two ports and configured to measure a concentration of a predetermined gaseous substance;
• a gas vessel having two ports and configured to accommodate the predetermined gaseous substance;
• a reference solution preparation vessel having two ports and configured to accommodate a predetermined liquid substance;
• pipe lines connecting the ports of the gas component detector, the gas vessel and the reference solution preparation vessel;
• and
• valves installed on the pipe lines,
• wherein the pipe lines and the valves are arranged and installed to form a first loop wherein the gas component detector is not connected to both the gas vessel and the reference solution preparation vessel, a second loop wherein the gas component detector is connected to the gas vessel and not connected to the reference solution preparation vessel, and a third loop wherein the gas component detector is connected to the reference solution preparation vessel and not connected to the gas vessel, and the valves switches between the loops.