Centrifuge Tube Conical Bottom

Quick Answer: The Centrifuge Tube Conical Bottom is a centrifuge tube whose base narrows to a point, so solids spun out of a liquid gather as a compact pellet at the tip. Conical bottom centrifuge tubes are the standard vessel for pelleting cells, bacteria and precipitates, and are most often made as 15 ml and 50 ml screw-cap plastic tubes.

Why the Cone Shape Matters

In a centrifuge, particles move outward and settle against the bottom of the tube. When that bottom is a cone, they are funnelled into a small point, forming a pellet that is easy to see and that stays in place while the liquid above it, the supernatant, is poured or pipetted off. That is why the conical bottom centrifuge tube is used for harvesting cells, collecting bacteria before DNA extraction, recovering precipitated DNA or protein, and concentrating urine sediment for microscopy.

Most conical tubes in use today are polypropylene with a screw cap and printed graduations along the side, which serve for approximate volumes; accurate measuring still needs a pipette or cylinder. The material, sizes and speed rating for this listing are not given in the title. Glass conical tubes exist as well, such as the Graduated Glass Centrifuge Tube, and are chosen when a solvent would attack plastic.

Tubes go into the rotor in balanced pairs. In a swing-out rotor the tube hangs vertically during the spin and the pellet forms neatly at the tip; in a fixed-angle rotor it smears slightly up one side, which is worth remembering when drawing off the supernatant. Compared with the round bottom tube, the cone gives a tighter pellet but is harder to mix and needs a rack to stand in.

Specifications

Applications

• Pelleting cells from culture medium before washing or counting
• Collecting bacteria from overnight broth cultures ahead of plasmid or DNA extraction
• Spinning down urine samples to examine the sediment under a microscope
• Separating soil, plant or food extracts from debris before analysis
• Recovering DNA or protein precipitates after alcohol or salt precipitation

Using Conical Tubes Correctly

• Balance tubes by weight in opposite rotor positions, and never exceed the tube’s rated speed
• Leave space below the cap, since overfilled tubes can leak under centrifugal force
• Stand tubes in a rack, because the pointed base cannot support them on the bench
• Check plastic tubes for cracks or crazing before reuse, and discard any that are cloudy or split

Why Choose LabEquip

Conical tubes are an everyday consumable for clinical laboratories, microbiology and biotechnology teaching labs and research groups that spin samples daily. LabEquip supplies them within Biology Lab Products; give the size, cap type and quantity through our contact page.

Frequently Asked Questions

Why use a conical bottom instead of a round bottom tube?

The cone gathers the spun material into a small, visible pellet at the tip, which makes it easier to remove the liquid without disturbing the pellet. Round bottom tubes spread the pellet more thinly but mix and resuspend more easily.

How full should a conical centrifuge tube be?

Fill to below the shoulder of the tube, leaving room under the cap, and never above the highest graduation. Overfilling raises the risk of leakage and makes balancing less accurate.

Are the printed graduations accurate?

They are intended for approximate volumes, such as judging how much supernatant remains. For volumes that must be accurate, measure with a pipette or measuring cylinder before adding the liquid to the tube.

Can plastic conical tubes be autoclaved?

Polypropylene tubes are generally autoclavable at 121 °C with the caps loosened, but repeated cycles can distort them. Polystyrene tubes cannot be autoclaved, so check the tube’s material and rating first.

Do these tubes fit every centrifuge?

They fit rotors or adaptors made for that tube size. A 15 ml tube needs a 15 ml bucket or adaptor and a 50 ml tube a 50 ml one, so compare your centrifuge’s accessories with the size you order.

Which chemicals can be used in plastic conical tubes?

Polypropylene tolerates water, aqueous buffers, alcohols and dilute acids and alkalis, and is routinely used for phenol-chloroform DNA extraction. Polystyrene is attacked by many organic solvents, so check the material before adding anything other than aqueous samples.

Last Updated: September 2026