- General Information
- Catalog & Data Sheets
- Publications & Protocols
Sample Volume and Probe Size
Selecting the proper probe size is important for optimizing sonication conditions. Each probe has an approximate recommended sample volume range. Sample vessel size and shape also determine the appropriate probe. For example, the ½” probe can process approximately 20-250mL. However, the ½” probe may have difficulty fitting inside a narrow vessel for a 20mL sample, so a microtip (probe with small tip diameter) may be a better option.
Microtips are recommended for small volumes (50mL or less) inside small, thin vessels. Since microtips are high intensity , and used with small sample volumes, they generate considerable heat within a sample. Therefore, microtips should be used for short processing times in a pulse mode to prevent overheating.
Larger volumes require larger probes for effective processing. A 1” probe will process a 1-liter sample faster than a ¾” probe. Using the proper probe size is key to reducing processing time and prolonging the lifespan of the probe. When processing samples of 1-liter or more, using a stir bar can increase a probe’s maximum processing volume for difficult samples.
Processing volumes are application specific. Sample volume range for any probe/horn is not absolute, but here is a general guideline to follow. Contact us for more details.
|Processing Volume Range
|0.2ml - 5ml
|1ml - 15ml
|10ml - 50ml
|20ml - 250ml
|50ml - 500ml
|100ml - 1,000ml
|1” with booster
|500ml - 2,000ml
Replaceable vs. Solid Tips
Replaceable tip probes are made in two pieces and have a separate tip with a threaded end that can be removed. As with all probes/tips, the tip will erode or wear out during normal use. Replaceable tip probes provide the option of replacing the tip instead of the entire probe.
Replaceable tip probes are used with aqueous samples only and should not be used in solutions containing organic solvents (other than water). Regardless of how tight the tip is connected, samples with alcohol, acetone or other low surface tension liquids, will seep inside the tip’s threading. Once inside, the tip will loosen and cause an overload error which will be displayed on screen. This will shut off sonication. Solid (1-piece) probes can be used for any sample type and will prevent this type of overload condition.
How to Safely Clamp a Converter
Improper clamping of the converter can damage the Sonicator system and void the warranty. The photo on the right shows the clamp attached to an active portion of the converter, which will hinder performance and potentially damage the Sonicator.
Note: Using a Qsonica sound enclosure or stand will ensure a proper fit.
Tip Depth / Foaming Issue
Probe tips must be submerged properly in a sample. If the tip is not submerged enough, the sample will foam, splash, or bubble.
Foaming often occurs with sample volumes below 1mL but can also occur with larger volumes, if the amplitude setting is too high.
If the tip is too deep, the sample will not circulate well and it will take longer to obtain good results. Some high amplitude probes will overload if placed too deep into a sample or too close to the bottom of the vessel.
Figure 1: Sample A will foam and will not process well. Sample B will not circulate the liquid effectively and will not process well. Sample C shows appropriate tip depth that will achieve good results in the shortest time.
Customers often place tubes in ice to control temperature, but it becomes difficult to see the tip’s depth in the sample. We recommend that you:
- Fill a tube with water to match the desired sample volume.
- Set the tube in the exact arrangement you’ll use during sonication and ensure the tube will not move (e.g. if ice melts).
- Insert the tip to ideal depth in the sample.
- Draw a horizontal line on the probe with a permanent marker to line up with the top of the tube. In doing so, you can easily replicate the same setup with the correct tip depth.
Vessel Shape and Size
A narrow vessel is preferred over a wide vessel. Ultrasonic energy is generated at the tip of the probe and directed downward. As a sample is processed, the liquid is pushed down and away in all directions. If a vessel is too wide, sections of sample further from the tip can remain untreated, so the sample does not mix evenly. A narrow vessel can process samples faster with twice the volume compared to a wider vessel. Regardless of vessel shape, the probe should never touch the sides or bottom of a vessel.
Power vs. Intensity
Power is the measure of electrical energy being delivered to the converter, which is measured in watts and displayed on the Sonicatorʼs screen. This electrical energy is transformed into mechanical energy in the converter. The piezoelectric crystals inside the converter are energized and move back and forth in a longitudinal direction. This conversion from electrical into mechanical energy causes a motion that travels through the horn/probe causing the tip to move up and down.
The distance of one movement up and down is called its amplitude. Amplitude is adjustable and each probe has a maximum amplitude value. For example, a ½” diameter probe at the 100% amplitude setting will achieve approximately a 120μm amplitude. At 50%, the amplitude is approximately 60μm. (Note: these values are approximate and not perfectly linear). Qsonica measures the amplitude of each probe at 100% and publishes these values in the brochure.
Amplitude and intensity have a positive correlation. A low amplitude setting will deliver low intensity sonication while high amplitude delivers high intensity. Amplitude, not power, is the most critical factor to reproduce sonication results. Several parameters must also remain constant to reproduce results, such as sample temperature, viscosity, and volume.
Power has a dynamic relationship with amplitude and intensity. For example, sonicating water at 50% amplitude requires less wattage compared to sonicating a viscous sample, such as oil. The amplitude and intensity are the same for both samples, but the power will differ because oil requires more wattage to drive the probe against a heavier load. In other words, the probe requires more energy to move through oil, so the system must work harder (use more power) to achieve the same amplitude.
Small fluctuations in the wattage display during sonication is normal. Major swings in wattage (+/-20 watts) may indicate a problem with the sample, setup or the Sonicator itself.Back to top
Nanomaterials and Probe Size
Certain applications, such as processing difficult nanoparticles, may require long processing times. Larger probes speed up processing and erode slower than smaller probes. Using a ½” diameter probe will process a 50mL sample much faster than a ¼” probe. The ½” probe will also cost less over time because the ¼” probe wears out faster and needs to be replaced more frequently.Back to top
1. All applications require optimization of amplitude and time settings. Test your probe with water using the same volume and vessel you will use for sample processing. Observe how the liquid moves during sonication at different amplitude settings. You should see and hear the activity in the water to the entire sample mixes and flows well.
2. Choose an amplitude setting that does not foam or splash the sample. Smaller volumes will require a lower amplitude setting and shorter pulses of sonication. Larger volumes can be sonicated at 100% amplitude, if necessary, to reduce processing times.
3. After choosing an amplitude setting, perform a time study by processing a sample at different time intervals then comparing results. Adjust amplitude and/or time to obtain the desired result.
4. See the Resources section on the website for protocols and papers from other customers.Back to top
There are many options for keeping samples cool during sonication:
- Use a pulse mode.
- Use ice along with the pulse mode.
- Use a Coolrack to chill samples and prevent movement.
- Chillers provide additional cooling capacity, if necessary.
- Standard probes are approved for liquids up to 140°F.
Cooling the Converter
Sonicating for long time periods causes heat buildup in both the probe and the converter. Overheating can severely damage the converter and Sonicator system. Many applications (such as using the Flocell) require continuous processing at high amplitude settings so steps must be taken to prevent overheating.
The converter should always remain at room temperature for safe operation. Attaching a compressed air hose with 10psig of filtered, dry air will ensure safe operation. See converter cooling in the addendum of the operator’s manual. Converter cooling is available for the Q500, Q700, or Q2000 models only. Q55 and Q125 models should be used in a pulse mode. Contact us for more details.
A booster is a device that increases the amplitude (intensity) of a 1” or ¾” probe. For example, a 1 liter sample may be processed twice as fast with a 1” probe and 2:1 booster when compared to the 1” probe used alone. The booster is recommended for processing difficult samples with volumes above 500ml.
Note: smaller diameter probes already offer very high intensity and will crack if used with a booster. Never use a booster with a ½” probe or microtip. Contact Qsonica to ensure the booster is compatible with your probe selection.Back to top
How to Determine Energy Delivered
The WATTS reading displayed on the screen is the amount of electrical energy the ultrasonic generator delivers to the converter.
NOTE: The greater the resistance to the movement of the probe, the greater the amount of power that will be delivered to the probe. As a liquid is being processed, its viscosity and chemical characteristics will change causing the power readings to fluctuate.
How to calculate the power that is being delivered to a sample:
- Turn on the equipment
- Set the amplitude as required
- With the probe in air, not immersed in a sample, record the amount of watts displayed on the power monitor
- Without changing the amplitude setting, immerse the probe into the sample and record the amount of watts displayed on the power monitor
- The difference in power readings between step 3 and 4, is the amount of power being delivered to the sample in watts
- To obtain the power density in watts/cm², divide the number of watts obtained in step 5 by the area of the probe tip.
Area = (diameter/2)² x π or π r²
Area using a 3mm probe: 3mm/10 = .3cm = .15cm radius
.15²cm X 3.142 (π) = .0707cm²
Now divide the number of watts by the area of the probe.
Using 1 watt as an example, the power density would be 1/.0707 = 14 watt/cm²
NOTE: The intensity is expressed as watts per surface area. (watts/cm²)Back to top
Sonication and Noise
Sonication produces high pitch noise (often exceeding 85dB), which can cause discomfort to the user and others nearby. A Sound Enclosure reduces noise by approximately 20dB. In addition to reducing the noise, Sound Enclosures have a built-in stand with clamp to hold the converter-probe assembly. No additional stand or clamp is required.