CLINICAL LAB SCIENEC

CHAPTER 8: PIPETTING AND USE OF GLASSWARE 191
A
B
FIGURE 8-7 (A) Glass and (B) polyethylene storage bottles for laboratory solutions.
Source: Delmar/Cengage Learning.
will not interact with chemicals. Bottles may be of varying sizes and some
have volumetric markings (Figure 8-7), although they are not normally used
for measuring solutions but rather for containing, storing, and shipping of
reagents, laboratory solutions, and patient specimens.
Pipettes
Selection of Pipettes
A pipette may also be classified as a pipette, pipetter (usually requires two parts,
the pipette tip and a mechanical device), or chemical dropper, and is a laboratory
instrument used to transport a measured volume of liquid. Pipetters may be
semi automated or may be operated by electrical means. Pipettes are commonly
used in chemistry and molecular biology research as well as for medical tests.
They are found in several designs for various purposes requiring differing levels
of accuracy and precision, from single-piece plastic pipettes to more complex
adjustable or electronic pipettes. All pipettes work by creating a vacuum above
the liquid-holding chamber and then selectively releasing this vacuum to draw
up and dispense liquids.
Pipettes that dispense between 1 μL and 1000 μL (1 mL) are termed
micropipettes, while macropipettes dispense volumes of liquid greater than
1 mL. Volumetric pipettes allow the user to measure one specific volume of
solution extremely accurately and then add it to another solution. They are
commonly used to make laboratory solutions from a base stock as well as
to prepare solutions for titration. Volumetric pipettes are typically marked
to indicate one single volume in a particular size pipette (similar to the construction
of volumetric flasks). Many different sizes are available. Specialized
syringes such as Hamilton syringes are used for small measurements in automated
equipment. These syringes measure materials in the microliter category
(1 microliter [μL] = 0.001 mL) and are used for the same purposes as pipetters
and pipetters. They may have multiple tips for handling several samples
simultaneously.
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