Pipette

November 1, 2021

The pipette is a volumetric instrument or measuring instrument. Although today’s pipettes are different from the first ones that emerged, their use can be traced back even 200 years. This is because the development of chemistry and other sciences that work with fluid analysis required measuring instruments for small samples.

The first patent for a volumetric pipette was registered in the USA in 1924. Although it is known that since 1790 pipettes were used; This was the first registered model and from that subsequent modifications were made to obtain the current pipette model.

One of the most innovative designs was that of Gilson pipetman in 1974 as they allowed volume adjustment. However, there were certain problems or limitations with these designs, mainly that they required a lot of force to be used, exerting great pressure at one end. The other drawback was the low resistance to high temperatures.

Starting in 1980, models began to be implemented to solve this type of complications, reducing the heating effect of the hand and applying spring or pressure mechanisms. Currently volumetric pipettes are in common use in various areas.

What is a Pipette?

A pipette is a volumetric instrument; In other words, it allows a measurement to be carried out, with it  the volume of substances is calculated . Although there are different capacities, they usually do not exceed 20 ml. It is made of plastic or glass, the latter being more common. It has a cylindrical and hollow shape to store the liquid.

The graduation that it has is in milliliters and according to its capacity they have a limit of error. Being the same as:

As you can see, the higher the capacity, the higher the error limit . This error represents the difference between the estimated volume and the actual volume; In this sense, the volumetric pipette is a systematic instrument and allows to foresee the error to compensate it if necessary thanks to its constancy in absolute value.

The volumetric pipette does not have in itself a graduation but a capacity; that is, a mark that indicates the volume that the pipette loads. The disadvantage of these pipettes is that they only load a certain volume but their advantage is precision, since they have a lower margin of error than graduated pipettes.

What is the Pipette for?

The pipette is an instrument used to measure the volume of liquids; It is a high precision instrument that measures the aliquot of a liquid; this is a proportional sample of it and as such it has the characteristics of the substance. Volumetric pipettes are used either to take these samples and measure them or to use them in various analyzes.

Uses of the Pipette

The main branches that use the pipette are chemistry, biology and medicine. It is used in analytical studies and in all cases where the precise measurement of a substance is needed, such as volumetry. Also in the preparation of solutions, since it is not only essential to have the necessary elements but also their proportion.

How is the pipette used?

Knowing how to use the pipette correctly is essential to have the exact volume of the sample to use. The first thing to do is make sure that the pipette is sterilized so as not to contaminate the sample. To extract the substance a propipette is used for suction.

It is usual to discard the first sample to ensure that the pipette has no residue. After taking the sample, the pipette is cleaned so that there are no external surpluses that can drain and affect the volume taken when transferring. Later you must make up the content.

Filling consists of leveling the liquid obtained with the gauging , when the meniscus of the liquid is flush with the gauging. Something very important to keep in mind in the flush is that you have to do it at eye level, otherwise an optical illusion is created that gives you the impression of agreement when it is not.

Pipette Calibration

There are two types of calibration for the volumetric pipette, the first is the calibration for pouring. In this the pipette indicates “TD”, “vert” or “ex”. The other type is the calibrated to contain , in which the pipette indicates “TC”, “cont” or “in.

The difference between these is that the volume indicated in the calibration to contain corresponds to the volume that the liquid has when it is in the pipette; while the calibration for pouring contains the volume of the solution poured, that is, it has the estimate of what adheres to the walls of the pipette.

The steps to perform a calibration are as follows:

    1. It is placed in distilled water and left at room temperature.
    2. A beaker is weighed, taking into account the error of one tenth of a mg.
    3. The pipette is filled with distilled water and transferred to the precipitate.
    4. The beaker is weighed to calculate the volume of the liquid.
    5. The process is repeated up to three times.
    6. The measure is calculated through the comparison in the measurements.
    7. The density of the water is calculated (temperature equal to those of the first measurements).

Calibration is understood as the determination of qualities. The volumetric pipette is calibrated to be used in a standard way, with a specific measurement and temperature; the temperature is usually 20 ° C; this temperature must be like this because the liquids undergo expansion with the change of temperature.

The volumetric pipette is used by professionals in areas that require analysis, measurements or transfer of volumes of liquids with great precision. Therefore it has a specific and detailed mode of use. However, it is easy to learn to handle it so you should not worry about it.

Types of Pipettes

There are several types of pipettes that correspond to different needs, such as the graduated pipette that has brands to take different volumes. Also the pasteur pipette that transfers liquids easily but without great precision. But when talking about volumetric pipettes, they are distinguished into two types, those that have only one capacity and those that have two.

The difference is that double gauge pipettes have more precision. It is used by making up the substance with the highest capacity and then letting it drain to the other level. Pipette types are classified by their level of precision and the difference in the volume they can load.

Pipette Features

The pipette is a cylinder usually made of borosilicate glass, with a conical tip and a certain capacity. In itself it is a simple and easy to identify instrument. Among its remarkable characteristics you find the blister that it has in its cylindrical body . This is the main aspect that differentiates the volumetric pipette from other types.

This blister is of a specific size as it indicates the volume it can hold, after the blister comes a narrowing at the bottom. This ampoule is of a different size depending on the volume loaded by the pipette. The other characteristic is the capacity, which can be one or two. When there is one, it is above the blister, if there are two, the other is below.

Importance of the Pipette

The volumetric pipette is the most efficient means to transfer liquid with an exact volume ; a necessity quite present in analytical research, in compounding and in various studies. Well, proportions are a fundamental element when working with solutions.

As is the volumetric pipette, there are a variety of pipettes and volumetric instruments to use in the laboratory and various instances; that adapt to different needs.

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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