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Pipettes are commonly used in laboratories to transfer milliliter volumes of liquids, from a minimum of 1 ml to a maximum of 50 ml. Straws can be disposable in sterile plastic or reusable in autoclavable glass. Both pipettes use a pipette to aspirate and expel liquids. Different sizes of pipettes are used in different experiments with the same pipette. For example, pipettes are important for mixing chemical solutions or cell suspensions, transferring liquids between different containers, or plating reagents at different densities. As long as careful attention is paid to the volume of liquid aspirated and expelled, pipettes can be a useful tool in the laboratory for accurately transferring milliliter volumes of liquid.

Types of pipettes and basic components of pipettes

Pipettes are usually sterile single-use plastic tubes; they can also be autoclavable, reusable glass tubes.

All pipettes use a pipette when pipetting.

The pipette eliminates the need for researchers to pipette by mouth as before. That primitive pipetting method is not recommended because it has the potential to cause serious consequences for liquids being sucked into the mouth.

A pipette ball is a type of pipette with the worst accuracy. It is usually paired with a glass pipette to transfer a variable amount of liquid.

Pipette pumps are also suitable for glass pipettes, which can transfer more precise liquid volumes. Pipette pumps are generally suitable for dispensing the same volume of liquid repeatedly.

Assistant pipettes are the most common pipettes. It consists of several main parts: the mouthpiece is where the pipette is inserted and where the filter membrane is placed, which protects the inside of the assistant pipette from contamination of the liquid.

Two buttons can be seen on the handle of the assistant pipette. When the upper button is pressed, the liquid is aspirated, and when the lower button is pressed, the liquid is discharged.

Most assistant pipettes also have a control knob for the liquid discharge rate. For example, it can be set to release the liquid under pressure, or it can be set for gravity release without external force.

While some assistant pipettes come with a power cord, most are battery powered.

Some assistant pipettes come with a stand that fits in the handle area, which allows the assistant pipette to be placed on its side when not in use without removing the pipette.

As mentioned earlier, the same pipette can use different sizes of pipettes depending on the volume to be pipetted, from as little as 0.1 milliliters to as many as tens of milliliters.

Basic operation of pipettes

First, choose the right size pipette based on the volume of liquid you want to transfer. Then open the package from the top, touch only the part above the tick mark, insert it into the tip of the pipette, and remove the remaining package.

Next, grab the pipette with one hand and open the lid of the container that contains the liquid you want to aspirate. Keeping the pipette upright, gently press the upper button to slowly aspirate your sample.

Use the graduated line on the pipette wall to measure the volume of liquid you want to transfer. Note that the volume should be read at the bottom of the meniscus, not the top.

Then carefully release the liquid into a container of your choice, taking care not to let the pipette tip touch any non-sterile surface.

Use caution and gentle force when expelling liquid, especially when using small volume capacity pipettes, to avoid contaminating the assistant pipette filter and sample, or damaging the assistant pipette. Mishandling when using an assistant pipette can annoy other more experienced people in the lab, who may have to take the pipette apart for repairs. When pumping large amounts of liquid or discharging liquid, the liquid transfer speed can be increased by pressing the button hard.

Finally, remember to properly discard the straw after transferring the liquid.

Application

Now that you know how to operate a pipette, let’s look in more detail at some common laboratory applications.

An important step when culturing and plating cells is uniform distribution of cells in the final solution. Cell suspensions can be mixed gently and efficiently using a pipette, which simultaneously mixes chemical solutions and reagents.

After isolation or processing of experimental cells, pipettes can be used to transfer whole cell clones for expansion or subsequent experimental analysis.