Micropipetting

Micropipetting

What's a Micropipette?

Tool used to measure and transfer very small volumes of liquid

Parts of a micropipette

• Plunger:
• Used to draw up and eject fluid
• Also twists to adjust the volume being measured
• Volume window - window on the side that shows you the volume that your micropipette is set to draw up
• Shaft - long extension that a tip is applied to on the end
• Tip - plastic piece that must be applied to the shaft of the micropipette before use
• Tip ejector -- button near the plunger that releases the tip after use

Types of micropipettes

In this class, we'll use a variety of micropipettes - each is able to measure and transfer a different volume of liquid.

Most of our micropipettes are the grey Edvotek ones.

• P10 measures 0.5 - 10 µL
• (µ = microliters -> there's 1,000,000 µL in a L!)
• P100 measures 10 - 100 µL
• P 1000 measures 100 - 1000 µL
• (1000 µL = 1 mL)

We also have green BIO-RAD P10 & purple Accumax P200

Using a micropipette

1. Set the volume to be measured/transferred
2. Add the appropriate tip to the end of the shaft
3. Depress the plunger until you reach the 1st stop
4. Insert the tip (only the tip!) into the liquid
5. Slowly release the plunger to draw the liquid up
6. Depress the plunger fully - through the 2nd stop to release the liquid
7. Use the tip ejector to release the tip (this needs to be done anytime you are measuring up a new liquid to prevent cross contamination. When in doubt, get a new tip).

Selecting a Micropipette

Choose the micropipette with a volume range that matches the volume of fluid you want to measure/transfer.E.g.

• If I want to transfer 60 uL of fluid, I should choose a P100 (measures 10 - 100 uL)
• If I want to transfer 5 uL of fluid, I should choose a P10 (measures 0.5 - 10 uL)
• If I want to transfer 450 uL of fluid, I should choose a P1000 (measures 100 - 1000 uL).

Setting the Volume

Twist the plunger to set the micropipette to the volume you want to transfer (you can see this in the volume window).

• Note: the grey edvotek micropipettes have a small locking mechanism (under the plunger/above the window) that you need to push UP to unlock prior to twisting the plunger.

Setting the Volume

The grey edvotek micropipettes have a line through the window. Treat this as a decimal point.

• Examples:
• Left: shows 50.00 uL
• Middle: shows 200.0 uL
• Right: shows 1.000 mL (remember - that = 1000 uL)

The green biorad P10s do not have a line, but do have a decimal point in the window The purple accumax only measures whole numbers

Choose a tip

• P10s use the small clear tips

• P100s (and P200s) use the yellow tips

• P1000s use the large blue or large clear tips

Don't use your fingers to take the tip out of the box, just push the end of the shaft onto a tip in the box. Be firm, but gentle - you will not hear a click

Measure and Transfer!

• Before you put the tip into the liquid you are measuring, press the plunger until you feel the first stop
• Then, put the tip into the liquid (do not submerge the shaft!)
• Slowly release the plunger to draw up the liquid (try to avoid bubbles)
• Remove the micropipette and place the tip against the side of container that you are transferring the liquid to (at about a 45 degree angle)
• Push the plunger all the way through the 2nd stop to release the liquid.

Eject the Tip

• Don't use your fingers to remove the tip.

• Instead, use the eject button to release the tip into a waste container (typically an empty beaker on your table).

Never do these things!

You should never:

• use a micropipette without a tip

• transfer a volume of liquid outside of the micropipettes measuring range

• tip the micropipette upside down/get liquid on the shaft