Pipettes are essential laboratory tools used for transferring liquids with precision. This guide covers various types of pipettes, including Beral, Pasteur, serological, and volumetric pipettes, detailing their specific applications and operational methods. Each pipette type is designed for different levels of accuracy and volume measurement, making them suitable for various laboratory tasks. Ideal for students and professionals in biology and chemistry, this resource provides insights into proper pipetting techniques and maintenance for optimal performance.

Key Points

  • Explains the differences between Beral and Pasteur pipettes for liquid transfer.
  • Describes serological pipettes and their use for quantitative transfers with vacuum sources.
  • Details volumetric pipettes designed for precise volume measurement with a single graduation mark.
  • Covers proper cleaning and maintenance practices for all types of pipettes.
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Biology
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4 pages
Biology
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TYPES OF PIPETTES
Beral pipette (commonly called a disposable pipette)
A Beral (disposable) pipette is typically made of plastic and
is used for non-quantitative transfer of solutions (filling a
cuvette for example). Sometimes these do have
graduations in the stem, but generally should never be used
when precise volume recordings are needed.
Pasteur pipette
A thin glass transfer pipette, similar in use and
limitations of a Beral pipette. A Pasteur pipette requires
a disposable rubber bulb to draw up solutions and
transfer them. The thin stem allows for more accuracy
than a Beral pipette in small volume transfers.
Serological pipette (similar but not identical to a Mohr pipette)
A serological pipette is used for
quantitative transfers. It requires a
vacuum source for transfer –
typically a pipettor or a pipette bulb
is attached to the blunt end.
Mouth-pipetting is always expressly
forbidden! The markings on the end
of the pipette are important to take
note of:
Graduations
The maximum volume of the
pipette and its graduations are
marked such as the following, which
means that the pipette is designed
to deliver a maximum of 10 mL and
that there are graduations to 1/10
th
of a mL. This also lets you know that
the 1/10
th
mL is known, so it is possible to estimate 1/100
th
mL.
Temperature
The glassware is calibrated to deliver accurate volumes at the stated temperature. Most liquids expand
somewhat with increasing temperature and contract with decreasing temperature. This is a very
negligible change for most measurements, so we generally do not consider the calibration temperature
unless the experiment calls for extreme precision.
TD or TC
Pipettes labeled TD (which stands for To Deliver and is sometimes marked as EX) at the upper end are
designed to deliver the volume stated on the pipette. There will always be a small amount of liquid
inside the tip after pipetting. If this liquid is blown out you will have delivered slightly more than the
designed capacity of the pipette. Almost all of our pipettes are TD pipettes. However, other types do
exist: Pipettes labeled TC (which stands for To Contain and is sometimes marked as IN) are designed to
contain the volume stated on the pipette. Therefore, all liquid on a TC pipette should be expelled to
obtain the desired volume. MOST of our pipettes are designed to deliver liquid volumes and as such as
TD pieces. MOST of our beakers and flasks are designed to contain liquids and are marked as TC pieces.
It is still a good idea to double check before using a piece of glassware.
Volumetric pipette
Volumetric pipettes or bulb pipette
allow the user to measure a volume
of solution extremely precisely
(precision of four significant figures).
These pipettes have a large bulb with
a long narrow portion above with a
single graduation mark as it is
calibrated for a single volume (like a
volumetric flask). Typical volumes are
10, 25, and 50 mL. Volumetric
pipettes are commonly used to make
laboratory solutions from a base
stock as well as prepare solutions for
titration. The markings are similar to
those of a serological pipette except
there is only one graduation for a
volumetric pipette.
All pipettes should be washed well immediately after using and given two to three final rinses with
distilled or deionized water and left to dry vertically in a drying rack. A pipette that is clean will not have
water spots or clinging droplets of liquid left.
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FAQs

What are the main uses of Beral and Pasteur pipettes?
Beral pipettes, typically made of plastic, are used for non-quantitative transfer of liquids, making them suitable for tasks like filling cuvettes. Pasteur pipettes, made of glass, offer more accuracy for small volume transfers and require a rubber bulb for operation. Both types are essential for laboratory work where precision is not the primary concern.
How do serological pipettes differ from volumetric pipettes?
Serological pipettes are designed for quantitative transfers and require a vacuum source, such as a pipettor, to function. They feature graduations that allow for precise measurement of liquid volumes. In contrast, volumetric pipettes are calibrated for a single volume and are used when high precision is necessary, typically featuring only one graduation mark.
What is the importance of cleaning pipettes after use?
Cleaning pipettes after use is crucial to maintain their accuracy and prevent contamination. Proper cleaning involves rinsing with distilled or deionized water and allowing them to dry vertically. A clean pipette ensures that no residual liquids affect future measurements, which is vital for experiments requiring precision.
What safety precautions should be taken when using pipettes?
Safety precautions when using pipettes include avoiding mouth pipetting, which is expressly forbidden due to health risks. Users should always employ pipette fillers or manual pipette fillers to ensure safe and accurate liquid transfer. Additionally, wearing appropriate personal protective equipment, such as gloves and goggles, is recommended to prevent exposure to hazardous substances.
What is the function of a pipette filler?
A pipette filler is a rubber bulb or manual device used to draw liquid into pipettes safely. It allows for controlled suction and dispensing of liquids without the risk of mouth pipetting. The design typically includes valves for precise operation, making it suitable for various types of pipettes, enhancing both safety and accuracy in liquid handling.

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