100-214-239 Rev. A A-3
Appendix A
Digital Sonifier
Minimizing Undesirable Factors
Some factors may be detrimental to enzyme or biological activity and can reduce the effective-
ness of ultrasonic processing. Minimize undesirable factors, as follows:
Foaming or Aerosoling
Always place the horn deep enough below the surface of the liquid to prevent violent motion
or agitation on the surface . This problem is more critical when processing small volumes (for
example, 0.3 to 5 ml). A conical-shaped tube or vial, such as a cut-down Eppendorf tube, is
recommended. The shape of this type of container raises the liquid level without increasing the
volume, thereby permitting the horn to be inserted more deeply below the liquid surface level.
Foaming can be detected by a change in the sound level and a fluctuating reading on the power
bar graph.
When aerosoling occurs, little or no energy couples reliably to the solution, and excessive top-
layer heating results. Remedy this problem by placing the probe as deep as possible and setting
the Amplitude control to 10% or 20% for a few seconds. Then gradually increase the Ampli-
tude control to the level required.
Discoloration of the Processed Sample
If the tip touch es the side of a glass tube or beaker, small glass particles are released, which
gradually changes the sample to a greyish color. Excessive tip corrosion can also cause a grey-
ing or darkening condition.
Sterilizing and Preventing
Cross-Contamination
You can sterilize horns and tips by removing them from the converter and autoclaving them.
It is faster, easier, and equally effective, however, to sterilize horns by immersing them in a bea-
ker of alcohol or other disinfectant and then turning the power on for a few seconds. This tech-
nique also removes unwanted residue from the horn and tip.
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