CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
Common Pipettes Used in the Clinical Laboratory
Semiquantitative Measurements
• Pasteur pipettes are used for semiquantitative measurements where the
amount being transferred is not critical. These pipettes are commonly
called droppers or “eye droppers” and are used for transferring small
amounts of liquids, often by drops. They are not graduated. Pasteur
pipettes may be made of either plastic or glass.
• Transfer pipettes are similar to Pasteur pipettes and are used for semiquantitative
measurements. They may be designed for larger quantities
than the Pasteur pipette is capable of transferring but can also be used
for measuring reagents by the number of drops dispensed. These pipettes
are made almost entirely from a soft plastic and their bulbs can serve as
a reservoir or liquid-holding chamber.
Quantitative Measurements
• Serological pipettes are measuring pipettes that provide a quantitative
measurement and have graduations extending all the way to the tip.
Some are designed as TD (to deliver) and contain a frosted band near
the end where a bulb might be placed.
• Mohr pipettes are measuring pipettes that resemble serological pipettes
and are used for quantitative measurements. The primary difference
between the basic serological pipette and the Mohr pipette is that the
graduations on the Mohr pipette do not extend all the way to the tip
(usually the last one milliliter). The Mohr pipette is used for “pointto-point”
measurements only and not for measuring to the tip of the
pipette.
• Micropipettes are extremely accurate for quantitative measurements for
measuring and transferring very small volumes, such as in patient samples
for testing. There are manual versions of the micropipette as well
as syringe-type micropipettes, which are found in sophisticated analytical
equipment. Manual micropipetters consist of two parts: the device
that displaces a certain volume of air and then pulls the same amount of
sample into the vacuum of a disposable micropipette tip. The measurements
are performed as a small fraction of a milliliter, called a microliter,
while reagents are measured in one or more milliliters. The term microliter
refers to 0.001 mL (μL). Micropipetters provide great accuracy as the
primary method for measuring patient samples for testing.
Quantitative Pipettes
Pipettes are designed in a variety of configurations that allow the pipetting of
extremely small volumes up to sizable amounts of liquids. These pieces of equipment
are usually open-ended glass or plastic tubes used to measure or transfer
fairly precise amounts of liquids. They may be either reusable or disposable;
increasingly, disposables are being used in clinical laboratories. Quantitative
pipettes measure volumes to a significantly accurate level. Pipettes that are
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