Graduated pipette: characteristics and price

November 2, 2021

Among the volumetric instruments used in laboratories is the graduated pipette . The purpose of the pipette is to measure an aliquot of liquid. This differs from the volumetric pipette in that the measurement is not specific for one measurement , but that it can be graduated to take several measurements.

The word pipette is originally from the French ‘ pipette ‘, which means ‘small tube’. Historical records reveal that the appearance of the pipette is close to the late 18th century in France . Records have also been found specifying the use of it during the nineteenth century. Pasteur is the one who receives the honor for the creation of the graduated pipette. However, today the pipette with his name has another design.

What is a graduated pipette?

It is a laboratory instrument with a cylindrical shape, generally made of pyrex or bosilicate glass . Its point is narrow in a conical shape and has a nozzle at one end. Its neck is much wider than that of the other types of pipettes. This has a graduation in milliliters. In general, its measurement ranges from 0.1 to 25ml .

The perfect measure for the volume of solutions is obtained at a temperature of 20ºC. The reason is because the change in temperature increases or minimizes the volume of liquids. For example, when the temperature rises, so does the volume; When the volume goes down, the temperature goes down as well.

It is the neck of the graduated pipette that provides the necessary information about the liquid to be studied. Its volume, divisions, substance temperature, and acronyms showing the required calibration. As for the acronym ‘ AS ‘ on the pipette, it is of utmost importance. These indicate the degree of precision of the instrument .

What is it useful for?

Generally, the graduated pipette is used for transferring and measuring liquid . In a basic sense, it does the same job as a volumetric pipette. The only difference is that the graduated pipette can measure various volumes. However, this causes a disadvantage to the graduated pipette, as it cannot accurately measure intermediate measurements .

For this reason, the most common use of the graduated pipette is to transfuse a proportion of the substance , instead of performing procedures that require precision. It is normal that many tend to confuse the usefulness of the graduated pipette with that of the burette. However, the difference between the two is very great.

As for the burette, it measures gases and liquids. For its part, the graduated pipette only measures liquids . On the other hand, the mechanism of the burette with a stopcock produces a less controlled release of the liquid compared to the pipette. Also, the purpose of the burette is another, which is why it can load larger amounts of liquid.

How does the graduated pipette work?

Graduated pipettes are an instrument created for laboratories. Therefore, they are used in these spaces. More specifically, in laboratories of medicine, biology and chemistry. Even the first pipette to be patented was intended to measure a series of amounts of blood and then carry out tests on it. Similarly, its use in these areas is usually very common, which is why it is used on a daily basis.

How to use?

Using a graduated pipette is not complicated. However, several aspects must be taken into account. One of them is the correct grip of the instrument. To do this, it must be taken from the top using the thumb and middle finger . The index finger will be the one who controls the expulsion of the liquid, for which it is only necessary to lift the finger.

To suck the liquid it is necessary to have a pump or propipette . This is a rubber pump, with a diameter that varies between 3 and 11mm. Its design is for pipette use only. This with the intention of preventing situations such as those that occurred in the past where the suction was done with the mouth. As a consequence, infections and poisonings were generated.

To use the pipette it is necessary to follow certain precautionary measures. The first thing is to leave the pipette inclined at an angle of between 10 and 20º after having expelled the liquid. It is also necessary to remove any excess liquid that remains on the tip after collecting the sample. But above all, you need to understand the specifications of the pipette. Otherwise, a bad measure would be taken.

Types of graduated pipette

The types of graduated pipettes can be differentiated thanks to the maximum volume that they can measure, also by the way of pouring. There are two types of discharge: Partial , which empties from line ‘0’ to the corresponding graduation line; and Total that is emptied to the tip of the pipette. In addition to pour types, there are also subtypes with minimal variations in pour specifications.

Serological pipette

This is a type of graduated pipette that is characterized by full pouring. There are two characteristics that stand out in the serological pipette: it is sterilized and its graduations reach the tip of the pipette. It has a maximum liquid volume capacity that is generally small. It is highly recommended for transfers from 5 to 25ml , however, 50ml pipettes are available.

Its use is usually very common in cell culture. But it is also used in any laboratory study where it is required to measure the volume of an aliquot of a sterilized substance . This in order to prevent any contamination or contact with another element that alters the aliquot values.

They are usually made of transparent polystyrene. It is a ‘ blow out ‘ type pipette so the liquid adhering to the walls of the pipette is not taken into account . To get rid of this ‘excess’ it is necessary to blow the pipette through the upper end where the hole that is also used for filling is located.

Graduated pipettes are generally compatible with pipetting instruments such as propipettes. In terms of precision, the maximum measurement is always the one with the highest precision , as with the smallest dimensions. When choosing which type of pipette to use, it is important to take into account what use it will be given and know how to read its instructions.

Characteristics of the graduated pipette

Since there is a wide range of pipettes, it is important to know the characteristics of the graduated pipette. Thanks to this, it is possible to distinguish it from other types of pipettes. Similarly, to be able to use this laboratory instrument correctly, it is necessary to know it. The pipette has a unique solid body, this avoids having to memorize different parts.

Material

Although there are presentations made of plastic, the graduated pipette is generally made of pyrex glass . This is a type of glass widely used for the manufacture of laboratory instruments thanks to its properties.

Dimensions

This is an aspect that depends on the pipette. It is possible to find pipettes up to 25ml. However, the most frequent are those of 0.5ml; 1.5ml; 5ml and 10ml.

Precision

The graduated pipette offers a much higher precision than the pasteur, but less than the volumetric one. However, the smaller the pipette, the more accurate the measurement will be . In the same way, its accuracy tends to grow in the last measure.

Graduation

The measurement is calculated in milliliters, this is equal to one thousandth of a liter. If the liquids taken with the pipette are at 20ºC, they correspond to 1/100 divisions. The meaning of this is the dimension that encompasses one division to another. Graduated pipettes usually have one to two gauges.

Difference between graduated pipette and volumetric pipette

  • The volumetric pipette has a gauging instead of a graduated scale.
  • The graduated pipette measures the volume of various liquids according to the range indicated on your body.
  • The volumetric pipette measures a single value and is much more accurate.

Differences between graduated pipette and burette

The common use of the buret within laboratories is to measure liquid volume. This is made up of two pieces: a long glass cylinder, with a hole in the upper part; and a stopcock on the lower level to control the flow of the liquid.

It has certain volumetric marks to make certain precise measurements of gas or liquid that you want to work on in a laboratory study.

The most striking differences between the burette and the graduated pipette are based on these aspects:

  • Burettes are instruments for measuring liquids and gases. The graduated pipette only measures liquids.
  • By having a stopcock, the burette has a different structure than the graduated pipette. The key on the burette makes emptying less accurate.
  • Regarding liquid containment, the burettes contain between 10 and 40ml. On the other hand, graduated pipettes work with smaller quantities.
  • Measurements in the burette are made from top to bottom. As a result, the initial and final volume is equal to the total of the liquid.

Importance of the graduated pipette

Within laboratory instruments, the graduated pipette is one of the fundamentals when measuring the volume of liquids . Thanks to this, the measurement process is streamlined, making it easier to have various measurements. As a result, it is not necessary to go to different models of pipettes, thus obtaining greater practicality when working in the laboratory.

Dr. Loony Davis5
 | Website

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.

Leave a Reply

Your email address will not be published. Required fields are marked *