TITLE: DISPENSING LIQUIDSUSING A PIPET
PURPOSE:The purpose of this Skills Training is to train the student in the proper way to dispense liquids using a volumetric, Mohr and/or Serological pipet and to teach the student Good Laboratory Practices (GLP’s).
PREREQUISITES: N/A
REFERENCES:
SAFETY EQUIPMENT: Gloves and safety glasses
MATERIALS:50 ml beaker
Volumetric pipet
Mohr – To Contain (TC) Graduated pipet
Serological – To Deliver (TD)Graduated pipet
Appropriate size and type of pipet transfer bulb or pump
Appropriate receiving vessel to pipet liquid into
Appropriate liquid for transfer
Box of Kimwipes
PROCEDURE:Proper pipetting for the delivery of liquids
1.PREPARE FOR THE TRANSFER OF A LIQUID
Determine which size and type of pipet is most suitable for transferring the desired liquid.
Pour the desired volume of liquid into the beaker from the original bottle. (Never pipet directly from an original bottle to prevent contamination of the liquid.)
Label the receiving vessel properly (See SOP – Proper Labeling)
Choose the appropriate pipet transfer bulb or pump and be sure it is in good working condition.
Place a piece of clean paper towel on the bench and place the transfer pipet on the paper (not on the bench itself).
Place a box of Kimwipes on the bench.
2.TRANSFER THE LIQUID
Make sure to prevent contamination of the liquid by paying full attention to your technique. If you are pipetting more than one liquid, you must have a separate pipet for each one, labeled so not to confuse them. If your liquid has health hazards, transfer the liquid in a fume hood.
IF USING A PIPET BULB FOR TRANSFER
Securely attach the pipet bulb on the top of the pipet making sure that it is sealed for the draw.
Collapse the pipet bulb to remove the air contained in the bulb.
- Place the tip of the pipet into the beaker of liquid.
- Carefully release the tension on the bulb allowing the liquid to be drawn into the pipet.
- Draw the liquid about a centimeter or so past the fill line. (DO NOT DRAW THE LIQUID INTO THE BULB – this is the major source of contamination!)
- Carefully and quickly remove the bulb and replace it with your finger.
- Carefully and slowly release your finger partially to allow the liquid to drip out of the tip until the bottom of the meniscus touches the top of the fill line. In the picture below, the volume is where the bottom of the belly of the meniscus just touches the top of the line that reads 2.5 ml. (reading top – down).
- Tightly keep your finger in place to hold the liquid.
- Once you have the accurate volume held in the pipet, lift the pipet out of the beaker.
- Wipe the tip with a Kimwipe and place the pipet into the appropriate transfer vessel
- If you are pipetting using a volumetric pipet:
- Remove your finger and allow the pipet to drain
- Touch the tip of the pipet into the receiving vessel to allow the last drop to be delivered.
- If you are pipetting using a Mohr pipet(TC – graduated pipet):
- Deliver the desired volume dispensing the liquid to the score line where the bottom of the belly of the meniscus just touches the top of the score line.
- Do not drain the pipet past the last score line, you will have an error in volume dispensed.
- If you are pipetting using a Serological (TD – graduated pipet):
- Deliver the desired volume dispensing the liquid to the score line where the bottom of the belly of the meniscus just touches the top of the score line.
- If all the volume is desired, drain the entire volume and blow out the tip using the pipet bulb.
- Remove all labels from the glassware and dispose.
Rinse the glassware with hot tap water and place into the washing vessel.
IF USING A PIPET PUMP FOR TRANSFER
- Hold the white bottom of the pipet pump while inserting the large bore end of the pipet into thehole
- With the tip of the pipet under the surface of the liquid hold the pipet and container at eye level,gently roll the pump wheel up to pull the solution up into the pipet.
- Pull the solution up until the bottom of the meniscus is at thevolume value desired (see image above).
- Once you have the accurate volume held in the pipet, lift the pipet out of the beaker.
- Wipe the tip with a Kimwipe and place the pipet into the appropriate transfer vessel.
- Roll the pump wheel down to dispensethe desired amount of solution from the pipet. See guidelines listed above for volumetric, Mohr, and Serological pipets.
- Holding onto the bottom of the pump, gently twist and pull the pipet out of the pump.
- Remove all labels from the glassware and dispose.
- If disposable, discard the pipet in the appropriate waste container.
- If not disposable, rinse the pipet with hot tap water and place into the washing vessel.
3.WASHING GLASSWARE
- Thoroughly rinse the glassware with hot tap water.
- Thoroughly rinse the glassware with distilled water, being careful not to turn the distilled water on to flow too fast as it will spray.
- Turn the pipet upside down to drain, or place into the pipetupside down in the pipetwash container located by the sink.
4.FINAL COMMENTS
NEVER PIPETTE BY MOUTH!
- Never lay the pipet down with liquid in it. Never allow the liquid to reach the cotton plug or toenter the pump or bulb.
Any chipped or cracked pipet must be disposed of in the glass waste container located in the lab.Notify your instructor.
TRAINING ASSESSMENT: The laboratory technician is considered skills trained in dispensing liquids using a pipetwhen they have successfully completed the training assessment.
- Receive 95% on all pipetting assessments.
DOCUMENTATION: Evaluations recorded in Skills Training Assessment Log placed in the laboratory notebook.
DOCUMENTATION OF SKILLS TRAINING:
Student Name: ______Approved By: ______
CCC Science Department Instructor / Date: ______
Date: ______
CCCLST0030 Approved: 30July2014 Revision: