8/16/2019 How to Use Pipettes

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Pipettes are used to measure and transfer liquid accurately. They function something like a

straw; the liquid is sucked into the pipette with a pipette aid (e.g. pipet pump or pipet filler).

There are two types of pipettes, volumetric and serological. Volumetric pipettes are more

accurate than serological pipettes.

Volumetric pipettes are designed to measure and transfer a predetermined volume of liquid.

For example a 5 ml. volumetric pipette has one marking on it. This marking measures exactly 5ml. of liquid, no more, no less.

In contrast, serological pipettes can be used to measure and transfer various amounts of liquid.

A 5 ml. serological pipette with one-tenth millimeter graduations can be used to obtain any

desired volume of liquid in one-tenth millimeter increments between 0.1 ml to 5.0 ml. Two kinds

of serological pipettes are commonly employed: blow-out (This is what we will use!) and drain-

out.Blow-out serological pipettes are graduated to the tip and have etched or colored rings around

the top. To obtain the desired amount, liquid in the tip of the pipette is "blown out". For

example, to accurately transfer 10 ml. of liquid using a 10-ml. blow-out pipette, liquid drains

from the "0" mark to as far as it will go on its own. The remaining drops of liquid are forced or

"blown-out" and included in the aliquot being measured, resulting in exactly 10 ml.  

Drain-out serological pipettes are not graduated to the tip and they lack colored or etched rings

(although they may have a color-coded rectangle or square to indicate the size of the pipette). If

you desire 10 ml. of liquid from a 10-ml. drain-out pipette, you allow the liquid to drain from

the "0" mark to the 10-ml. mark and discard the rest of the liquid. 

Pipette aids such as the pipet pump are used because mouth pipetting is risky andshould not be attempted no matter how safe the chemical seems.

Pasteur pipettes are somewhat of a misnomer because they are merely droppers, (plastic or

glass). Exact measures of liquid cannot be taken with a Pasteur pipette, although some are

graduated in .5 to 1mL increments for rough masures.

top of TD pipetbottom of TD pipet

bottom of blow-out pipet top of blow-out pipet

pipet pump

Volumetric pipet: just 1 volume 

Serological Pipet

TD (to deliver) style) or drain-out style

We currently do not have any to use.

Pasteur Pipet aka: a dropper in glass or plastic

Serological Pipet

(blow-out style)

this is what we use

in class, mostly

How to Use a Pipet! What are the Various Types of Pipettes!