Centrifuge
Centrifuge Action
 Centrifugal force is an outward force created by fast
spinning. The greater the velocity the greater the force.
 Causes material to separate into layers according to
weight. Heavier material settles to the bottom while the
lighter liquid portion (called supernatant) rises to the
top.
 Heavier particles require less force to make them settle.
Lighter particles require greater centrifugal force or
gravity to settle.
Centrifuge Balance
 Load so the Rotor will spin evenly around the drive shaft
o A rotor is balanced by placing samples and their
containers symmetrically in the rotor
o Place tubes of similar weight opposite each other
o Tubes/vials across from on another should be a
nearly equal weight (weight not volume)
o Manufacturer specifications will instruct you on how
close the weight of the opposing tubes must be to the
sample weight, such as 0.5 g
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When equally weighted containers/vials of test material
are not available use tubes of water
Centrifuge Safety:
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Balance Load
Use stoppered or covered tubes
Close centrifuge during use
Never open centrifuge before spinning is complete
and has stopped
Disinfect daily when used with body fluids
Centrifuging Blood results in layers of:
RBC, WBC, Platelets, Plasma (serum)
Centrifuging Urine results in:
Cells, crystals, casts, debris (collect as sediment at the
bottom). The sediment is examined under a microscope.
Balance the load for 3 serum tubes
Balance the load for two conical
tubes of urine
Proper clean up of centrifuge if tube breaks:
1. Let the centrifuge “rest” for 10 to 15 minutes to allow all
aerosols to settle.
2. Spray the inside with 10% bleach, let sit for a few minutes
to inactivate the biohazardous materials
3. Wearing proper PPE, carefully remove any broken glass
and dispose of it in a broken glass container
Definitions
Agar
An extract of red algae used as a culture medium
Autoclave
Device that uses steam under pressure to sterilize reusable
items
Coverslip
Small glass square used to cover liquid specimens on
slides to protect the microscope and to stabilize the
specimen being examined
Cuvette
Clear glass container, made to specific optical standards
for photometric and colorimetric analysis. Generally 1 cm
x 1 cm. When using the cuvette must be free of
fingerprints, scratches. The test fluid must be free of
bubbles. Wipe with lab glassware tissue
Incubator
Cabinet used to keep cultures warn – usually set at human
body temperature which is 37 C
Petri Dish
Round, flat clear glass or plastic dish with a fitted cover.
Dish contains a gel like medium on which microorganism
or cell growth can take place.
Device used to thoroughly mix solutions to a uniform
consistency. Examples: Vortexer, stir plate, hot plate
with stirrer
Supernatant The liquid portion of a fluid that has been centrifuged.
Mixers
Cleaning Glass and Plastic Ware:
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As soon as possible after use, soak glass and plastic
ware - in a disinfectant solution such as weak
bleach if contaminated with microorganisms, dye,
or human body fluids
Wash by hand using the commercial lab detergent
and bottlebrush as needed
Rinse items thoroughly with tap water
Rinse in distilled water to remove any chlorine or
chemicals in the tap water
o Remaining traces of chemicals can cause
inaccurate tests results in future use
Dry in a dry heat oven or autoclave if available