| CPC G01N 30/32 (2013.01) [G01N 30/14 (2013.01); G01N 2030/027 (2013.01); G01N 2030/146 (2013.01); G01N 2030/326 (2013.01)] | 9 Claims |

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1. A pump unit of a chromatograph including a separation column, the pump unit comprising:
a pump that pumps a mobile phase through a flow path to the separation column; and
a metal ion trap including a filter element provided at a position farther downstream than the pump in the flow path between pump and the separation column, wherein
the pump includes a metal member that comes into contact with the mobile phase, and
the filter element includes a metal ion retention structure for retaining metal ions by interacting with the metal ions eluted into the mobile phase due to contact between the metal member and the mobile phase.
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