Within pipette calibration, there are five widely used grades of pipettes, all of which have specific guidelines and requirements regarding use, testing, maintenance, and measurement. The five grades of pipettes include disposable/transfer, graduated/serological, single-channel, multichannel, and repeat pipette. From the most basic transfer pipette dropper to the advanced repeat dispensing pipettor, the manner in which the equipment is handled will impact the accuracy of the test results.
At Pipettes.com, we pride ourselves on the compliance-oriented calibration service we provide our clients, but part of our expertise involves having in-depth knowledge of all the instruments we service. This post will define the various types of pipettes and how to use them to ensure your tests provide the most precise results with the smallest margin of error:
This is the most basic type of pipette; it is not a sophisticated piece of lab equipment and can be used for rough measurements only. However, when using a disposable pipette, it’s important to follow a standard pipetting technique. Always use a new pipette and dispose of it after testing, aspirate liquid at a 90-degree angle, dispense at a 45-degree angle, and touch off to make sure all the liquid is dispensed.
When using this type of pipette, the final volume is found by calculating the difference of the liquid level before and after the liquid is dispensed, much like a burette. This is the standard technique for using a graduated pipette:
Hold pipette in solution, don’t touch the bottom. Squeeze the bulb and attach it to the top of the pipette. Hold forefinger on top of pipette to control volume aspiration. Subtract the amount needed into a separate beaker while staying eye level to assure proper measurement.
Measure solution from the bottom of the meniscus, the crescent-shaped surface of the liquid that is visible in the pipette. Subtract needed volume from the initial volume and find the volume needed to release to in order to get the desired amount.