Table of Contents
Advertisement
10. FREQUENTLY ASKED QUESTIONS
Probe size vs. Sample volume
Selecting the proper size probe is a critical factor when sonicating a sample. The sample
volume to be processed must correlate with the tip diameter. Each probe has a recom-
mended sample volume range. This range may overlap with other probes.
For example the 1/8" probe is recommended for approximately 500 µL to 15 mL.
Depending on the application and type of sample, you may be able to process a volume
outside of our recommended range.
Small volumes require a small tip diameter. Small probes (¼" or less) are recommended
for processing samples inside small, thin vessels such as microcentrifuge tubes. These
small probe sizes are high intensity and made for short processing times. Using a small
probe tip for long time periods will generate a considerable amount of heat. Pulse mode
should be used to reduce heat buildup.
While there is no absolute sample volume range for any probe/horn, below is a general
guideline to follow. Using a sample volume outside each tip diameter's range is
normally not recommended. Processing volumes are application specific.
Vessel shape and size
A narrow vessel is preferable to a wide vessel. The ultrasonic energy is generated from
the tip and is directed downward. As a sample is processed the liquid is pushed down
and away in all directions. If the vessel is too wide, it will not mix effectively and some
sample will remain untreated at the periphery. The probe should never touch the sides
or bottom of the vessel.
How to prevent foaming (small sample issue)
Foaming is a problem that often occurs with samples volumes below 1ml. The cause of
foaming is generally 3 issues: amplitude is too high for a small volume, tip is too large
for the volume, or the tip is not inserted to a proper depth.
Tip depth
The depth of the probe within the liquid is an important issue. If the probe is too close
to the surface of the liquid, it can create foam. If the probe is too deep, it may sonicate
against the bottom of the vessel and not effectively processing the sample. The sample
must flow freely below the tip in order to be mixed effectively. Without effective
mixing you cannot ensure the entire sample volume will pass below the tip and become
processed.
Tip Diameter
5/64" (1.6 mm)
1/8" (3.2 mm)
1/4" (6.4 mm)
Processing Volume Range
200 μL to 5 mL
500 μL to 15 mL
10 mL to 50 mL
Advertisement
Table of Contents
