An atomic absorption spectrophotometer in which a holder is removably fitted to a block, the holder holding a tube for heating a sample as a result of flow of a current, the holder being provided with a through hole, the atomic absorption spectrophotometer comprising:
- a fixed portion provided around a virtual axis that extends in a direction of fitting of the holder to the block, a front side being a front with respect to the direction of fitting of the holder to the block and a rear side being rear with respect to the direction of fitting of the holder to the block, the fixed portion being fixed to the block while the fixed portion is located at a distance on the front side of the holder;
- a movable portion provided around the virtual axis, the movable portion configured to abut on the front side of the holder by moving over an outer side of the fixed portion along the virtual axis while the movable portion is located on the front side of the holder;
- a first female thread portion formed in an inner circumferential surface of the fixed portion from the rear side toward the front side;
- a small-diameter portion having an inner diameter smaller than a minimum diameter of the first female thread portion formed on the front side of the inner circumferential surface of the fixed portion with respect to the first female thread portion;
- a second female thread portion having a minimum diameter larger than a maximum diameter of the first female thread portion is formed on an inner circumferential surface of the movable portion from an end on the rear side toward the front side,
- wherein the through hole is configured to receive a first bolt inserted into the through hole in the direction of fitting of the holder to the block in a first state and to receive a second bolt inserted into the through hole in the direction of fitting of the holder to the block in a second state;
- the first bolt including a first male thread portion and a shaft portion,
- the first male thread portion being located on the front side of the first bolt, the first male thread portion having a maximum diameter smaller than the minimum diameter of the second female thread portion, and configured to be fitted to the first female thread portion,
- the shaft portion being located on the rear side of the first bolt and having an outer diameter smaller than the minimum diameter of the second female thread portion,
- wherein, in the first state, the first male thread portion is fastened to the first female thread portion so that the first bolt presses the holder from the rear side of holder toward the front side of the holder;
- and
- the second bolt including an abutment portion and a second male thread portion,
- the second male thread portion configured to be fastened to the second female thread portion with the abutment portion abutting on the small-diameter portion in the second state,
- the abutment portion being located on the front side of the second bolt and having an outer diameter smaller than the minimum diameter of the first female thread portion and larger than the inner diameter of the small-diameter portion, and being able to abut on the small-diameter portion of the inner circumferential surface of the fixed portion,
- the second male thread portion being located on the rear side the abutment portion and being fitted to the second female thread portion of the inner circumferential surface of the movable portion,
- wherein, in the second state, the movable portion is moved toward the holder to press the holder from the front side toward the rear side.