Sonics VC70T - Manual (Page 14)

moving cells circulate repeatedly below the probe. Solid materials however have a
tendency to be repelled by the ultrasonic, and should be processed in a vessel large
enough to accommodate the probe, yet small enough to restrict sample movement. For
small samples, conical shaped test tubes are recommended. Although plastic tubes work
well, glass and stainless steel tubes usually work better than plastic ones.
Allowing the probe to contact the vessel will decrease the power output, and cause
minute grey glass particles to migrate into the sample. Although these glass particles will
not adversely affect the chemical composition of the sample, they will form a thin grey
layer on centrifuging. If the probe has to come in contact with a solid sample, use a
standard 20mm (3/4”) diameter stainless steel centrifuge tube cut to 70mm (3”) length.
Do not use a glass tube. Microtips must never allowed to come in contact with anything
but the liquid, because the stress resulting at the point of contact with a hard surface will
cause the microtip to fracture. Although larger probes will not fracture if they come in
contact with a glass vessel, they may cause the vessel to fracture.
Before each application, place the tip in water or alcohol and energize the power supply
for a few seconds to remove any residual substances.
If concerned with sample loss in test tube due to sticking, siliconize the test tube as
follows: Wash and dry the test tube thoroughly, coat with silicone, then air dry.
“Sigmacote” manufactured by Sigma Chemical Co., 3050 Spruce Street, St. Louis,
Missouri 63103, USA, phone (314) 771-5765, is ideally suited for that purpose.
Probes may be autoclaved, or sterilized by immersing in boiling water or in a detergent
bactericide and a disinfectant.
High viscosity and concentration are problematic. 5,000 cps and 15% concentration by
weight are maximum limits. Because with ultrasonics the sound waves are propagated
through the sample, if the sample is so thick that it will not pour or circulate easily, it is
too thick for ultrasonic processing.
Use the Continuous Flow Cell for processing large volumes. This accessory is
recommended for the treatment of low viscosity samples, which do not require extended
exposure to ultrasonics. When working with temperature sensitive sample, circulate the
sample through a coiled tube immersed in a salted ice bath to minimize the temperature
elevation that takes place within the cell.
Use the Cup Horn for processing pathogenic, radioactive, and biohazardous materials in
complete isolation without probe intrusion. Because plastic tubes have a tendency to
absorb vibrations, it is preferable to contain the sample in a stainless steel tubes or glass
tubes when working with a cup horn. To expedite processing, add glass beads to the
sample. If desired, crushed ice can also be added to the water inside the cup horn, in order
to optimize cooling. Processing samples in a Cup Horn will usually take 3 to 4 times
longer than processing with direct probe intrusion.
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