flasks –Erlenmeyer flasks are used primarily toprepare
solutions prior to an accurate volume adjustment. Although there are volumetric
markings on these flasks, they are not calibrated and should not be relied upon
for exact volume measurements.
B) Beakers –Beakers
are also used for preparing solutions,especially when a pH adjustment requires
access to the solution by a pH probe. The volumetric markings on beakers are
also not reliable.
C) Graduated cylinders –Graduated
cylinders are calibrated withsufficient accuracy for most volume measurements
when preparing solutions. For example, the calibration of most 100 mL graduated
cylinder can be relied upon to accurately measure to within +/- 0.6 mL.
D) Volumetric flasks –Volumetric
flasks are used to measure aspecific volume with the highest degree of
accuracy, and areused to make standard solutions for analytical assays. For
example, the calibration of a 100 mL volumetric flask can have an accuracy of
+/- 0.1 mL.
E) Pipets –Pipets
are glass or plastic devices that are routinely usedto measure and transfer
liquids by drawing the liquid into the tube with a bulb or mechanical pump.
pipets are small glass tubes used with a bulb to transfer volumes as small as a
single drop and as large as a few mL. They are not graduated and are not used
to measure volumes.
pipets (transfer pipets) are plastic pipettes with a bulb at one end used for
transfer of liquids. Sometimes they have calibration marks, which have a low
level of accuracy. They are often disposable, sterile and individually wrapped.
or “blowout,” pipets are graduated glass tubes used to measure anywhere from
0.1 to 50 mL. When the liquid has drained from this pipette, the final drop in
the tip is transferred with a puff of air.
or “to deliver,” pipets are similar to blowout pipettes, but do not require a
puff of air to accurately deliver the desired volume. They can be identified by
the label ― “TD” on the top.
pipets are not graduated, but are carefully calibrated to deliver a single,
highly accurate volume, and are used for the transfer of exact volumes.
micropipettes are mechanical pumps calibrated to deliver highly accurate
volumes generally less than 1.0 mL, and as little as 0.1 microliters. They are
often adjustable for measuring different volumes and they always use
dispensable plastic tips to actually transfer the liquids
Multichannel micropipettes can deliver
the same volume from as many as 12 tips simultaneously. All automatic
micropipettes need regular maintenance, calibration, and validation.