APPENDIX 4.a

USING THE PIPET

A pipet is designed to deliver a specific volume of a liquid. Three kinds of pipets are commonly used: · volumetric pipet- delivers a fixed volume of liquid · measuring (Mohr) pipet- calibrated to deliver a variable volume of liquid · Oswald-Folin pipet-delivers a fixed volume (blow-out last drop) Note: Pipets marked TD (to deliver) do not require blow-out. Pipets marked TC (to contain) require blow-out.
To pipet a liquid, keep the index finger of your dominant hand near the mouth of the pipet. Place the pipet tip into the liquid container. Do not let the tip touch the bottom or sides of the container.
Using your other hand, squeeze the rubber bulb and place it over the mouth of the pipet. NEVER USE YOUR MOUTH TO DRAW LIQUID INTO THE PIPET!
Release the bulb slowly in order to draw a specific volume of the liquid into the pipet. The liquid level should be about 1-2cm above the calibration mark. For large volume pipets, you may need to repeatedly use the bulb to draw enough liquid. DO NOT LET THE LIQUID ENTER THE BULB. THIS MAY CONTAMINATE THE LIQUID AND PREVENT THE BULB FROM OPERATING PROPERLY.
Quickly remove the bulb and simultaneously place your index finger tightly over the mouth of the pipet to prevent any liquid from escaping. Now slightly move your finger in order to release the liquid until the meniscus is even with the calibration mark.
Place the pipet, with your finger still on the mouth, over the container to which you will transfer the liquid. Release your finger and let the liquid drain completely out of the pipet. If some of the liquid remains in the pipet tip, do not blow into the pipet to force the liquid out (for TD pipets). The pipet is calibrated to deliver an accurate volume in spite of some liquid remaining in the tip.	Note: Some Liquid Remains in the Tip