A graduated pipette is a pipette that has its volume marked over the entire length of the tube. They are necessary to measure with great precision and to perform the transfer of a liquid from one container to another.
They are usually made with plastic or glass materials, they have a conical-shaped tip. Have maracas in all its extension, these indicate the existing volume of a point to other.
With small pipettes it is possible to obtain a more accurate measurement of the fluids, on the other hand, with a large pipette it is possible to carry out measurements when the requirements in precision they are not so critical.
Accordingly, pipettes vary in volume, with most measuring between 0 and 25.0 milliliters (0.00 and 0.88 imp fl oz; 0.00 and 0.85 US fl oz).
- What is a graduated pipette?
- Uses of graduated pipette
- Pipette types
- Graduated pipette precision
- Graduated pipette vs volumetric pipette
- Difference between graduated pipette and a Burette
- Difference between graduated and volumetric pipette
- Graduated pipette function
- Manufacturers of graduated pipettes
What is a graduated pipette?
Historically, the accuracy of a graduated pipette was not as good as that of a volumetric pipette (accuracy of 3 significant figures); however, with manufacturing methods improved, the accuracy indicated by the manufacturer may be equal to that of a volumetric pipette.
Experts note that graduated pipettes have higher accuracy than the Pasteur pipette. Have tolerances ranging from ±0.6% to ±0.4% of nominal volume when measured at 20 °C (68°F).
Graduated pipettes are manufactured in accordance with ISO specifications for the accuracy and arrangement of graduation.
Grade A and AS pipettes they have the highest accuracy, while the S stands for "delivery fast». These allowed margins of error are identical to those of the DIN EN ISO standards.
Grade B pipettes they usually have twice the error compared to grade A pipettes and AS. These pipettes commonly come in volumes of 5, 10, 25 and 50 ml.
Some have been developed varieties of propipetters [clarificación necesaria], both manual and electrically assisted.
Originally pipettes were made of sodocalcium glass, but currently many are made of borosilicate glass; disposable graduated pipettes are often made of polystyrene.
Uses of graduated pipette
- Volume Measurements: The primary purpose of a graduated pipette is to accurately measure and transfer specific volumes of liquids. This is crucial in various scientific experiments and analyses where precise quantities of reagents, solutions, or samples are required.
- Titration: In titration experiments, where a solution of known concentration is gradually added to another solution to determine its concentration, graduated pipettes are used to deliver precise volumes of the titrant solution.
- Sample Preparation: In fields like chemistry, biology, and medicine, researchers often need to prepare solutions with specific concentrations or volumes. Graduated pipettes enable the preparation of such solutions with high accuracy.
- Quality Control: Industries such as pharmaceuticals and food production require stringent quality control measures. Graduated pipettes are used to accurately dispense ingredients or additives, ensuring the consistency and reliability of the final products.
- Cell Culture: In cell culture work, researchers need to transfer exact volumes of cell suspensions, growth media, and reagents. Graduated pipettes are crucial for maintaining consistent conditions and avoiding errors in these processes.
- DNA/RNA Analysis: Genetic research often involves working with small volumes of DNA, RNA, and enzymes. Graduated pipettes are used to handle these materials accurately during procedures like polymerase chain reaction (PCR) and gel electrophoresis.
- Microbiology: In microbiology labs, graduated pipettes are used to inoculate cultures, dispense media, and transfer samples. This precision is essential to ensure accurate results in studies of microorganisms.
- Chemical Analysis: In analytical chemistry, where the accurate measurement of substances is critical, graduated pipettes are used to prepare standards, dilutions, and calibration solutions.
- Environmental Testing: Environmental labs utilize graduated pipettes for water and soil sample preparation, ensuring that accurate amounts of reagents are added to test samples.
- Educational Purposes: Graduated pipettes are often used in educational settings to teach students about accurate liquid handling techniques and measurements in scientific experiments.
There are two pipette types that differ depending on the location of the markings with reference to the tip of the pipette, these are: Mohr Pipettes and Serological pipettes.
Its further differentiation significant is in the position of the first graduation mark to be find it closer to the tip of the pipette.
On the other hand, the pipettes graded are classified into types ranging from one to three.
- The type 1 and type 3 pipettes they have the nominal value at the bottom (zero at the top). However, when it comes to the type 1 pipette, the solution for all volumes is delivered so partial.
- Type 2 pipettes have the nominal value at the top (zero at the bottom) and the solution is fully supplied for any volume.
- For type 3, the solution is fully supplied only to the nominal value.
Graduated pipette precision
So what is the precition of a pipette:
- Class A Precision: These pipettes have a high level of precision and are designed for critical laboratory applications where accuracy is of utmost importance. Class A pipettes are often calibrated to meet strict standards and may have a precision within ±0.05% to ±0.20% of the nominal volume. They are used in analytical chemistry, pharmaceuticals, and other precision-oriented fields.
- Class B Precision: Class B pipettes have a slightly lower precision compared to Class A pipettes. They are typically used in general laboratory work and may have a precision within ±0.5% to ±1.0% of the nominal volume. While they are less precise than Class A pipettes, they are still suitable for many laboratory applications.
- Disposable Pipettes: Disposable pipettes, often used in educational settings and some less critical applications, may have lower precision. Their precision can vary, but they are generally less accurate than Class A or Class B pipettes.
It's important to note that the precision of a graduated pipette can also be influenced by factors such as the user's technique, environmental conditions (temperature, humidity, air pressure), and the quality of the pipette itself. Regular calibration and proper maintenance are essential to ensure that a pipette maintains its specified precision over time.
Graduated pipette vs volumetric pipette
The volumetric pipettes are they are used to transfer an exact amount of liquid with high accuracy. Your margin of error at 20 degrees Celsius is +/- 0.02 mL (varies according to the manufacturer, class and size).
They are used to transfer anything from 1 mL to 50 mL and when accuracy is of the utmost importance.
Micropipettes are also a type of volumetric pipettes. They also have a high accuracy, but they they are used to transfer very small amounts of liquid, often less than 1 mL.
It is usually more accurate using a volumetric pipette to transfer large amounts of liquid because if a micropipette is used several times to transfer the same amount in fact, the error is spreading.
Those with multiple channels (tips) are often used in fields such as microbiology/biochemistry when so many samples have to be prepared at the same time. They are more efficient.
Difference between graduated pipette and a Burette
They can be used for transfer liquids, but they are mostly used in titrations, in which no it is known what volume is going to be needed at the beginning.
Can control the flow of the liquid using the stopcock. You can open it completely to allow a continuous flow or set it to drip one drop at a time. One drop is
Flow control is what allows burettes to be used in titrations. You can slowly add a desired amount of liquid until it reaches its equivalence point and measure the amount of liquid you have dispensed.
Difference between graduated and volumetric pipette
Volumetric pipettes transfer a lot of solution, very accurately. They can only be used for the liquid supply for which it has been calibrated.
This type of pipettes has narrow tips and in the center there is an expansion that resembles the bulb type. In the section of the tube, above the central expansion, you can see the calibration mark, the only one that this type of pipettes has.
Graduated pipette function
These types of pipettes are used for the accurate measurement and transfer of liquid volumes of a container to another. They are usually made of plastic or glass and their
tip is conical.
In the following video you will be able to appreciate the correct use of the pipettes and the precautions that must be taken into account.
Manufacturers of graduated pipettes
- Gilson: https://www.gilson.com/
- Eppendorf: https://www.eppendorf.com/
- VWR: https://us.vwr.com/
- Sartorius: https://www.sartorius.com/
- Thermo Fisher Scientific: https://www.thermofisher.com/
- Mettler Toledo: https://www.mt.com/
- Corning: https://www.corning.com/
- Rainin Instrument: https://www.rainin.com/
Please note that these links may not be available in all regions, and that the availability of specific products may also vary based on your location.
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