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Techniques Lab A ext: Practice with Viscous Solutions

Enzyme and DNA solutions are often thick and viscous due to high concentrations of protein, DNA or a stabilizing agent such as glycerol. Viscous solutions require extra care in pipetting in order to deliver accurate amounts of sample and to not waste precious materials.

To refine your pipetting technique, working with tiny volumes and viscous solutions.

Materials per team
   Solution A, colored glycerol solution       rack for reaction tubes
   P-20 micropipet and yellow tips container for waste

-Set pipet volume only within the range specified for that micropipet.
-When using a micropipet, first apply a tip.
-Always keep a micropipet in a vertical position when there is fluid in the tip.
-Use your thumb to control the speed at which the plunger rises after taking up or ejecting fluid.


-When FILLING the pipet tip, push down the plunger to the FIRST STOP and hold it there.
-Lower the tip just below the surface of the liquid to be sampled. Ease up on the plunger SLOWLY so the sample is carefully drawn into the pipet tip.

-Remove the pipet tip from the sample. OBSERVE the volume of sample in the tip. NOTICE if it is a small amount, tiny amount, or teeny-weeny amount...

-Pick up the tube or locate waxed paper for dispensing liquid. Position the tip to barely touch the receiving surface.

-SLOWLY push down plunger to the FIRST STOP. THEN SLOWLY push down the plunger to the SECOND STOP to deliver all the sample.
-HOLD THE PLUNGER DOWN AT THE SECOND STOP WHILE moving the pipet away from the sample.

Activity      Teacher Notes

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