Graduated Pipette

November 1, 2021

The graduated pipette is a volumetric instrument . Like the volumetric pipette , the graduated pipette is an instrument used for the measurement of an aliquot of liquid; with the difference that it is not for the specific measurement of a measure, but thanks to its graduation it can take several of them.

The term pipette comes from “pipette”, a French word that was adopted to mean “small tube”. There is evidence of the existence of the pipette from the end of the 18th century in France and there are records of its use throughout the 19th century. The creation of the graduated pipette is attributed to Pasteur, although the one that currently bears his name has another design.

What is a Graduated Pipette?

The graduated pipette is a pyrex or borosilicate glass cylinder with a tapered, narrow tip and a nozzle at the end; having a wider neck than other pipettes. The graduation it has is in milliliters , commonly measuring 0.1 to 25 ml.

The measurement of the volume of the solutions corresponds to a temperature of 20 ° C because with changes in temperature the liquid increases or decreases its volume. For example, when the temperature rises it increases and when it decreases the volume does the same.

The neck of the pipette will provide you with the information you need to know about it. Its volume, divisions, the temperature at which the substance must be and the acronyms that indicate the type of calibration required. The inscription “AS” on the pipette is really important, as it refers to the degree of precision and fast delivery.

What is a Graduated Pipette for?

The graduated pipette is used to measure and transfer liquid ; It basically works like the volumetric pipette, with the difference that it has the ability to measure different volumes; Of course, this has the disadvantage that intermediate measurements have a lower level of precision.

For this reason, they are mostly used to transfer an aliquot of the substance; rather than to perform procedures that require great precision. Many tend to confuse the function of the graduated pipette with that of the burette; but there is a significant difference.

The burette measures gases and liquids, while the graduated pipette only liquids. In addition, the burette mechanism with a stopcock makes the release of the liquid much less controlled than that of the pipette. The burette has another purpose of use, and therefore can load larger amounts of liquid.

How does a Graduated Pipette work?

Graduated pipettes are laboratory instruments and as such are used in these; specifically those of chemistry, biology and medicine . In fact, the first patented pipette was made in order to measure certain amounts of blood to perform tests on it. Likewise, its use in these areas is extremely common, using it even daily.

Uses of the Graduated Pipette

The use of the pipette is simple but certain things must be taken into consideration, such as the correct grip of the instrument , which is done by taking it from the upper part between the thumb and the middle finger; leaving the index to control the expulsion of the liquid. This expulsion is done by lifting the index finger.

The suction of the liquid is carried out with a pump or propipette; This is a 3 to 11mm diameter rubber pump specifically designed to be used in pipettes. This to avoid incidents such as those that occurred previously when sucking with the mouth, generating infections and poisoning.

The use of the pipette requires certain precautionary measures such as leaving the pipette tilted at an angle of 10 to 20 ° after expelling the liquid. Also clean the excess that remains on the tip after collecting the sample; and mainly understand the specifications of the pipette; Otherwise the measure could be taken wrong.

Types of Graduated Pipette

The types of graduated pipettes differ mainly in the maximum volume that they can measure and in the type of discharge. There are two types of spills , partial that empties from line “0” to the corresponding graduation line, and total that empties to the tip of the pipette. Within the discharge types there are subtypes that vary minimally in the discharge specifications.

  • Serological Pipette

The serological pipette is a type of graduated end-pour pipette. This pipette has two distinctive qualities: it is sterilized and has graduations up to the tip of the pipette. Its maximum liquid volume capacity tends to be small, it is recommended for the transfer of 5 to 25 ml; although they can come from up to 50 ml.

The serological pipette is used in cell culture and in any type of laboratory activity that requires the measurement of the volume of an aliquot of a substance under sterilized conditions, to avoid any type of contamination or contact with other types of elements that could alter the aliquot. .

They are made of transparent polystyrene and are of the “blow out” type , which means that they do not take into consideration the part of the liquid that remains adhered to the walls of the pipette. To expel this, it is required to use the blowing method and for this it has the open upper end, which is also used for filling.

Graduated pipettes are generally compatible with pipetting instruments such as propipettes. In terms of precision, the maximum measurement is always the most precise and also the smallest. The most important thing when choosing what type of pipette to use is to take into consideration what we are using it for and understand its indications.

Characteristics of the Graduated Pipette

Due to the variety of existing pipettes, knowing the characteristics of graduated pipettes is necessary to distinguish it from other types of pipettes. Likewise, using the instrument correctly depends on knowing it. The pipette has a single solid body that makes it up, so you don’t have to remember different parts.

  • Material

Although you can find it made of plastic; the graduated pipette is made mostly of pyrex glass. Glass with which many laboratory instruments are made thanks to its properties.

  • Dimensions

This point depends on the pipette. They are up to 25 ml but the most used are 0.5 ml, 1.5 ml, 5 ml and 10 ml.

  • Precision

The precision of the graduated pipette is greater than that of the pasteur and less than the volumetric one. The smaller the pipette, the more precision it has in the measurement; likewise, its accuracy increases in the last measurement.

  • Graduation

The measurement is taken in milliliters, a measurement that refers to one thousandth of a liter. This commonly with liquids at 20 ° C corresponding their divisions to 1/100, this means the dimension that covers from one division to another. Graduated pipettes can have one or two gauges.

Graduated pipettes bring their characteristics in the same pipette in detail so that at the time of use you can check the relevant information there. One of the most important points is the type of pouring of the pipette, which is also checked by seeing if it has a capacity or double , otherwise you could pour it affecting the measurement.

Importance of the Graduated Pipette

The pipette is an extremely important instrument for measuring the volume of liquids in the laboratory and the graduated pipette facilitates and streamlines the measurement process by having different measurements in itself; without having the need to resort to many different models of pipettes, thus giving practicality to laboratory work.

There are several types and subtypes of pipettes, designed for different uses and needs and even outside of these there are other volume measuring instruments that are used in a variety of areas.

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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