Homogenization seeks to create samples in which analytes of interest are dispersed uniformly throughout. Numerous technologies can achieve this, including pressure, mechanical (rotorstator or blade-type), and bead-beating.
Mechanical homogenization is based principally on mechanical shear and the disruption of structures that include tissues from plants, animals, or humans. This mechanical breakdown is assisted to some degree by cavitational forces. Regardless, the operational variables for mechanical homogenization are time, rotor speed, and rotor type.
Ultrasonic homogenizers rely exclusively on cavitation, a phenomenon that has drawn a lot of attention for chemical synthesis. Cavitation involves sound waves traveling through fluids that create microscopic bubbles that expand and then collapse violently, attacking and disrupting nearby cells and structures.
Mechanical homogenizers have a reputation for breaking samples down to nanometer-sized particles, and this is certainly true for long, high-speed runs. But as Holly Yacko Archibald – sales director at PRO Scientific (Oxford, CT) – notes, breakdown into almost any particle size domain is possible. “It’s possible to gently mix samples by running for a few seconds at low speed, which will provide a broader particle size bandwidth.”
Another misconception involves the alleged inability to process very small sample sizes, an important consideration as samples become more valuable. Mechanical probes have no problem processing samples even in 0.5 mL tubes, assures Ms. Archibald.
Since mechanical homogenizers resemble kitchen blenders, some cost-conscious lab managers assume that a $12 appliance will perform as well as a homogenizer. While that may be true for some easily processed samples for which precision and reproducibility are nonissues, dedicated homogenizers hold several trumps over blenders.
Mechanical homogenizers use precision-crafted stainless steel rotors and probes that are easy to clean, chemically resistant, and autoclavable. “And their results are reproducible,” Ms. Archibald adds.
Some instruments incorporate both ultrasonic and mechanical homogenization modes.
The main advantage of dual-mode homogenization is the ability to reach submicron particle sizes rapidly and reproducibly while mitigating somewhat the drawbacks of both modes. Mechanical and ultrasonic homogenization occur sequentially: First, mechanical disruption handles the larger-sized particles, then the ultrasonic probe turns on to complete the process. Alternatively, users may use either mode alone.
Since ultrasound tends to heat samples through cavitational effects, it’s not always suitable for heat-sensitive samples. Dual-mode homogenization minimizes sample contact with ultrasound, thereby sparing labile analytes from long exposure to ultrasound.
“Users should consider what they are trying to homogenize, and how small they need their samples to be,” says Tracy Christian, marketing coordinator at IKA Works (Wilmington, NC). Achieving submicron particle sizes involves either ultrasonic disruption or bead milling. The former is faster but is noisy, tends to heat the sample, and can sometimes alter its chemical characteristics.
According to Ms. Christian, other desirables include:
• easy cleaning of product-contact surfaces
• a low motor noise, since homogenizers are usually located on workbenches close to operators
• ease of use
• rapid homogenization
• user control over homogenization parameters through a familiar digital display
• low heat generation
• a programmable library of methods
Omni Bead Ruptor 24
- Simultaneously homogenizes in either 24 x 2mL or 12 x 7mL tubes
- Whisper Drive Technology delivers ultra-quiet motor operation
- No cool-down required between processes: Processes hundreds of samples per day
- 99 programmable memory settings
- Disposable tubes ensure no threat of crosscontamination or sample degradation
IKA T 25 Digital
- For volumes of 1 to 2,000 ml (H2O)
- Rotor-stator process has delivered proven results for 30 years
- Multiple stainless steel dispersing elements are available with a variety of rotor/stator configurations for a wide range of applications or disposable plastic dispersing tools
- Works well with highly viscous substances, up to 5,000 mPas
- Standard version offers digital display
KINEMATICA POLYTRON® PT 10-35GT
- LED speed indication for better reproducibility
- Low noise level, for better working environment
- Quick coupling, adapting more than 30 different generators
- High performance motor, for even the toughest samples
- 5 year warranty, we stand behind our products
- Combines full automation of mechanical and ultrasonic homogenizing into one unit
- Allows the use of each homogenizing method dependently or independently of each other within a programmable or manual mode
- Contains a brushless motor for mechanical homogenizing and 130-watt processor for ultrasonic
- Able to process up to 20 samples in one run