Pipetting | Environmental Health & Safety (2024)

FAQs

What are the safety rules for pipetting? ›

Never put a pipette in your mouth. Draw the liquid into the pipette using a rubber bulb or pipette pump. Never withdraw a liquid from a near-empty container. If you attempt to fill a pipette under conditions where air can enter the pipette, the liquid will shoot up into the bulb or pump.

Do not ever use your mouth to pull the liquid into a pipet. This is the most common method of becoming poisoned in a chemical laboratory or becoming infected in a clinical laboratory. Mouth pipetting is forbidden in the chemistry department. Do not allow the solution to be drawn up into the bulb.

From this standard, the average percentage error of a good quality pipette (range 1 – 10,000 µL) is 1.55% (systematic error) and 0.95% (random error).

Pipetting modes

Two pipetting techniques are used in the lab: forward mode (also known as standard mode) and reverse mode. For pipetting most aqueous solutions, forward mode should be used. It typically yields better accuracy and precision than reverse mode and is used by manufacturers to calibrate their pipettes.

Never point a pipette up. This may cause liquid to run down into the pipette destroying it. When withdrawing liquids with the pipette, always release the plunger slowly. This prevents liquid from rushing into the end of the pipette and clogging it up.

Depress the plunger to the first stop, immerse the tip into the liquid, and aspirate by releasing the plunger. Remove the pipette from the liquid and depress the plunger to the second stop to dispense the entire contents.

Many lab workers pipette for longer periods each day. Typical symptoms include pain in the thumb (De Quervain's syndrome), forearm and elbow (tendonitis or tenosynovitis), trigger finger, finger pain (digital-nerve injury), and shoulder pain.

Pipetting Precaution

First of all, remember do not pipette if the tip is not installed. At the beginning of the sample pipetting operation, it is necessary to keep it slow and stable by preventing the sample from entering the solution extractor, in case of the occurrence of air leakage due to the excessive speed.

What is the largest source of pipetting problems? ›

Pipettes should be given a quick clean every day. To clean your pipette daily, wipe the outside surfaces with 70% ethanol. Pipettes should also have a deeper clean, performed at least every three months.

Put the pipette—held at 10–45 degrees—against the wall of the receiving chamber, and smoothly depress the plunger to the first stop. Wait one second and then depress the plunger to the second stop. Slide the tip up the vessel wall to remove the pipette. Allow the plunger to return to its rest position.

The general principle of using a pipette is that the user will set a volume to aspirate (pull in) and dispense (push out). Liquid is pulled into an attached pipette tip, which is uniquely chosen for the volume being handled.