The Centrifuge

Question 1

What is the centrifuge used for?

Answer 1

Separating particles in a suspension from a liquid.

Question 2

How does a centrifuge work?

Answer 2

Centrifugal force forces heavier objects outward and forms sediment at the bottom of the tube. Lighter weight fluid is left on the inside (top of the tube).

Question 3

What is the lighter weight fluid left on the top of a tube after spinning called?

Answer 3

Supernatant.

Question 4

What are the two types of centrifuge tube?

Answer 4

Conical and round bottomed.

Question 5

Is a conical bottomed tube used for high or low speeds?

Answer 5

Low.

Question 6

Is a round bottomed tube used for high or low speeds?

Answer 6

High.

Question 7

What are the three types of centrifuge?

Answer 7

Angle head
Swing-out head
Microhaematocrit

Question 8

Describe an angle head centrifuge.

Answer 8

• Tube slots are at a set angle – usually 10 – 60 degrees from vertical

Question 9

What is the advantage of an angle head centrifuge?

Answer 9

• Advantage = higher speeds and faster separation

Question 10

Describe a swing-out head centrifuge.

Answer 10

• Tube buckets swing freely - starting vertically and moving to a horizontal position during spinning

Question 11

What is the advantage of a swing-out head centrifuge?

Answer 11

• Advantage = more solid pellet which is less likely to be disturbed when
  removing the supernatant

Question 12

What four sample types can a centrifuge be used to prepare?

Answer 12

• Urine – sediment microscopy
• Blood – separate cells from plasma/serum for biochemistry
• Blood - Microhaematocrit – PCV and TP/TS (total protein/total solids)
• Faeces for flotation

Question 13

List how to safely use a centrifuge. (8 steps)

Answer 13

1. Position the centrifuge on a firm base.
2. Place each tube carefully in the tube slots
3. Make sure the centrifuge is balanced – place an identical tube with the same volume of sample or water in the opposite slot.
4. Make sure the guard bowl is free from debris
5. Apply the safety plate if needed
6. Close and lock the lid
7. Set the appropriate time and speed for the sample being spun
8. Start the motor

Question 14

What do you do if the centrifuge starts to make an unusual noise?

Answer 14

Stop it immediately.

Question 15

What do you do if breakages occur?

Answer 15

• WAIT 10 minutes before opening the lid in case of aerosol formation
  of the sample
• Remove broken glass and clean

Question 16

Can you touch moving parts of the centrifuge?

Answer 16

No.

Question 17

How should you care for the centrifuge?

Answer 17

• Firm stable base
• Annual service (some)
• Cleaned regularly
• Some may need lubrication
• Turn off before cleaning