A good suction head depends on concentricity, taper, and importantly absorption.

1 taper: if the taper of the filter element suction head is good, the match with the gun is very good, and the suction will be more accurate;

2. Concentricity: Concentricity refers to the vertical circle at the nozzle and the connection between the nozzle and the straw. If it is not the same center, it means that the concentricity is not good.

3. Adsorption: adsorption is related to the material of the suction head. If the material of the suction head is not good, it will affect the accuracy of the pipette, resulting in a large amount of liquid residue or simply hanging on the wall, resulting in pipette error; So in the selection of filter element suction head to pay special attention to the above three points.