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12. 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 recommended
sample volume range. This range may overlap with other probes. For example,
the 1/8” probe
is recommended for approximately 1-15ml. 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 micro centrifuge 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.
Tip Diameter
Processing Volume Range
1/16" (2mm)
0.2ml - 5ml
1/8" (3mm)
1ml - 15ml
1/4" (6mm)
10ml - 50ml
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.
The probe should be submerged approximately halfway into the liquid but there are exceptions.
Before processing actual samples, it is recommended to test the probe in a vessel filled with
water to observe the ultrasonic energy and the flow pattern of the liquid. During this test you
can adjust the probe’s depth until you see adequate mixing and movement of the water.
Power vs. Intensity
Power is the measure of the electrical energy that is being delivered to the converter. It is
measured in watts and displayed on the
processor’s screen. At the converter, the electrical
