graduated pipette

November 2, 2021

In a laboratory it is necessary to take exact measurements of liquids, for this, graduated pipettes are used, a glass or plastic material that are calibrated in small divisions to measure different amounts of liquid.

What is it?

It is a straight glass or plastic tube with a narrowing at one end, known as a conical tip, and at the other end it has a mouthpiece. They are calibrated in small divisions to measure different amounts of liquid, between 0.1 and 25 ml.

They have a wide neck, which makes it less accurate than the volumetric pipette. It is used to take volume of solutions where high precision is not required. They are used in laboratories to measure volume or transfer quantities of liquid from one container to another.

They are divided into two types: Mohr or subterminal pipette and serological or terminal pipette, the first has a graduation along the finished tube before the tip and the second has measurements up to the tip.

Characteristics of the graduated pipette

They are made of plastic or borosilicate glass (pyrex). On their body they have lines that indicate volume. The most common numbers for measurement are 0.5 ml, 1.5 ml, 5 ml and 10 ml.

On its neck are the specifications such as: Maximum volume, size of the divisions, calibration temperature and legend identified as TD or TC which mean in English: To delivery (ex) or To contain (in), that is, pour or empty respectively.

For example: The inscription “10ml in 1/100 TD 20 ° C” indicates that it is calibrated in divisions of 1/100 and that it pours up to 10 ml with liquids at a temperature not higher than 20º.

Small volume pipettes provide accurate measurement while larger volume pipettes do not provide as much precision.

How are they used?

  • It should be held in the upper third, between the thumb and the middle finger.
  • The final measurement or total capacity is more precise than the intermediate measurements, so you must choose the pipette that has the maximum measurement indicated for the exact volume to be measured.
  • To collect the liquid to be measured, place the pipette about 6 mm from the bottom of the container. The liquid should not be sucked in with the mouth, a propipette or pump should be used, when we reach the required volume we cover the mouthpiece with the index finger.
  • When the liquid is already in the pipette, it should be placed at an angle of 10 to 20 °.
  • The index finger is lifted to release the liquid.

Differences between graduated pipette and volumetric pipette

  • The volumetric pipette has a gauge and not a graduated scale.
  • The graduated pipette allows you to measure the volume of different liquids according to the range indicated on your body.
  • The volumetric pipette allows you to measure a single value.
  • The volumetric pipette is more accurate.
Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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