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A Guide to Choosing the Right Mixer for Your Laboratory

Lab mixers allow you to easily mix samples in containers like test tubes. There are a lot of considerations when buying a new laboratory apparatus for mixing and stirrer. What’s the viscosity of the liquid you’ll be mixing? What are your requirements for torque, horsepower or rotational speed? We’ll take a look at what you’ll need to know to choose the right mixer.

Laboratory Mixers: What to Consider

Laboratory mixers are either digital or analog. Digital mixers offer more control (i.e., they let the user select a precise temperature and speed) while analog mixers are controlled via simple knobs and lack a readout screen to report the exact speed or temperature.

When using a mixer without a temperature indicator, use a stand or clamp system that suspends the thermometer in the liquid and prevents it from touching the container’s walls. This helps to ensure an accurate temperature reading. DLAB offers a universal plate stand for mixers and stirrers.

When selecting a mixer, note that maximum volumes are based on water. Depending on the viscosity of the liquids to be used, the actual volume may vary. Viscosity is measured in cycles per second (cps).

For lab mixers, speeds are typically measured in revolutions per minute (rpm). Many units offer variable speed operation.

For convenience, some Velp Scientifica mixers feature an IR sensor that automatically senses tubes and mixers and operates without pressing additional settings.

Types of Laboratory Mixers

Magnetic Mixers

Velp Scientifica Multi-stirrer

Magnetic mixers, also referred to as magnetic stirrers, mix liquids by use of a magnetic stir bar inside the container. Non-metal beakers like glass are used to prevent interference with the magnetic field. Magnetic mixers are often used in microbiology and biochemistry.

They can cleaned down easily and efficiently and are generally easy and simple to use. Because there is only a small stir bar that comes into contact with liquid, there is also reduces the risk of cross-contamination. This makes it a good option if you are planning on mixing more than one type of solution.

A magnetic stirrer may not be powerful enough to adequately stir more viscous liquids, so consider the kind of solution you will be mixing before buying.

We’ve previously talked about the differences between magnetic mixers and overhead stirrers.

Thermal Mixers

DLAB HM100-Pro Thermal Mixer

Thermal mixers – also called thermal shakers – function not only as orbital mixers (with a shaking motion), but also to keep samples at a specific temperature. The devices are available with different-sized PCR (Polymerase Chain Reaction) plates that ensure consistent, precise thermal transfer when used in conjunction with test tubes, containers and other microplates.

Vortex Mixers

Vortex mixers, which may also be called vortexers, uses an electric motor to drive a cupped rubber piece in an oscillating cylindrical motion. A test tube or other container is placed into the rubber cup, transferring the motion to the liquid inside and creating a vortex (basically, a swirl of liquid), which mixes the sample. Its uses range from gentle shaking to high-speed mixing.

Vortex mixers are generally small in size, which is beneficial when working in a smaller space. They can also be extremely efficient as well, thanks to their high RPM.

Velp Scientifica Classic Vortex Mixer

The vortex machine – available in either digital or analog models – is often used in bioscience, microbiology, biochemical and analytical laboratories for processes such as suspending cells and mixing either reagents of an assay or mixing experimental samples with a dilutant.

Spinning: Vortex Mixers Versus Centrifuges

While vortex mixers and centrifuges both employ a spinning motion, that’s where their similarities end. Vortex mixers combine substances, while centrifuges separate them. The object that spins is also different. With the mixer, the test tube containing the liquid spins; with the centrifuge, the test tube is held in a fixed position within a rotor, which spins in the centrifuge.

For more information on centrifuges, check out our previous blog.

Sonic Supply offers a wide range of mixers and stirrers from manufacturers such as VELP Scientifica and DLAB. If you have any questions or need help selecting the right mixer for your lab, call or email us. We’re here to help!

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