Chapter 3 Notes

Chapter 3 Basic Skills of the Biotechnology Workplace Measuring volumes: Volume is a measurement of the amount of space something occupies. Unit : Liters (L), milliliters (ml) or microliters (µl) 1 ml = 1/1000 L 1 µl = 1/1000 ml Depending on the volume to be measured instruments used may be a. graduated cylinders b. pipets c. micropipets Measurement in the science lab is done in the metric system which can be calculated in multiples of ten. If a scientist is measuring volumes greater than 10 mls he will use a graduated cylinder. For volumes under 10 mls and down to 0.5ml, a pipet is used. When pipeting always use a pipet pump to fill and empty the pipet. The pipet pump will evacuate the air in the pipet forming a vacuum that causes the liquid to rise in the pipet. For volumes less than 1ml, a micropipette is used. A micropipette measures in µl or microliters which are one thousandths of a ml.

Picking and using the appropriate micropipette P-100 or P – 200 micropipette Used for measurements from 100 µl to 10 µl and between 200 µl and 20 µl respectively.

The plunger can sit at any one of three positions:

Position 1 is Position 2 is reached by Position 3 is reached where the pipette pushing down on the plunger by pushing down is at rest until resistance is met from position 2

To Draw Up Liquid To remove the last drop of liquid from the tip, push down to Position 3. If delivering into a liquid, remove the tip from the liquid before releasing the plunger Hold the micropipette with the thumb resting on the plunger and the fingers curled around the upper body.

Keeping the plunger at the second position, place the tip attached to the end of the micropipette beneath the Push down surface of the liquid to be drawn up. Try with the not to push right to the bottom thumb until (especially if you are removing Position 2 is supernatant from a centrifuged pellet), reached. but ensure that the tip is far enough below the surface of the liquid that no air is drawn up.

Steadily release pressure on the plunger and allow it to return to Position 1. Do this carefully, particularly with large volumes, as the liquid may shoot up into the tip and the body of the micropipette. If bubbles appear in the tip, return the liquid to the container by pushing down to Position 3 and start again (you may need to change to a dry tip).

Making solutions Making solutions is one if the most common jobs in the lab. Most solutions made will be aqueous solutions where water is the dissolving agent or solvent, and the substances are being dissolved are the solutes.