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Bi1x_2009_W1_S1

Bi1x_2009_W1_S1 - Bi 1x Spring 2009 Week 1 Session 1...

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Page 1 of 6 Bi 1x, Spring 2009 Week 1, Session 1 Pipetting Working with bacteria Spectrophotometry Pipetting One of the most important instruments in a biology lab is the pipettor, a device that allows highly accurate handling of small quantities of liquid. There are several brands of pipettors in the lab, but they all operate in the same manner, relying on air displacement to move liquid in and out of disposable plastic tips. Pipettors are manufactured to handle different volume ranges, and it is important to choose the appropriate pippetor for the volume of liquid you wish to deliver to ensure accurate results. You will have been provided with a set of micropipettors consisting of a combination of the following list of volume ranges: Pipettor model Recommended Volume Range Tip P-2 0.2 – 2.0 µ l Clear P-10 0.5 – 10.0 µ l Clear P-20 2 – 20 µ l Yellow P-50 5 – 50 µ l Yellow P-100 10 – 100 µ l Yellow P-200 20 – 200 µ l Yellow P-1000 100 – 1000 µ l Blue You have also been given one large volume pipettor. The type of pipettor differs from group to group; some groups have electric transfer pipettors (to be used with long, disposable plastic pipettes) and others have large volume micropipettors. Using a Micropipettor 1. Select the model of pipettor that is appropriate for the volume you wish to dispense (consult the above table, if necessary). 2. Set the volume by rotating the plunger button until the desired volume appears in the display window. Remember that regardless of the volume, pipettors have three digit displays—the digits represent different volume increments. 3. Attach a fresh tip by pressing the bottom of the pipettor shaft down into the top of the tip. Do not apply excessive force! 4. Press the plunger down to the first stop. 5. Keeping your pipettor vertical, immerse the tip 2-4 mm into the liquid. 6. Slowly allow the plunger to return to the up position.
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Page 2 of 6 7. Wait 1 or more seconds to allow the entire volume of liquid to flow into the tip (you will have to wait longer for more viscous fluids). 8. Withdraw the tip from the sample. 9. To dispense the sample, dip the tip into the recipient solution and slowly depress the tip to the first stop, mix (if necessary) by moving the plunger up and down, then depress to the second stop. This will “blow out” any remaining liquid in the tip. If you are pipetting into an empty tube, touch the tip to the side of the wall while dispensing. 10. Withdraw the tip from the sample, and eject it into the appropriate waste container by pushing the eject button. Using a large volume pipettor - If you have been given a macropipettor (a large volume micropipettor), you use it in exactly the same way as a micropipettor, only with larger tips.
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