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Purchasing Guide: Stirrers and Mixers

Stirrers and mixers are used for mixing a variety of samples in the lab

by Lab Manager
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As you’d expect, stirrers and mixers are used for mixing a variety of samples in the lab, and there are numerous options available depending on what you’re mixing and the volume you’re working with. Some applications are suited to a magnetic stirrer, which relies on a rotating magnetic field to rotate a stir bar within the liquid. Magnetic stirrers are available with heated or non-heated platforms. Overhead stirrers with a drive motor to power the impeller are better suited for more viscous liquids or larger volumes. For a list of stirrer and mixer manufacturers, see our online directory:

8 Questions to Ask When Buying a Stirrer or Mixer:

  1. What sample volumes will you be working with?
  2. What is the intended application? Magnetic stirrers are best suited to applications that require low shear mixing.
  3. How viscous are the samples? Highly viscous samples may create too much resistance for a magnetic stirrer.
  4. What mixing speeds are required?
  5. Is a heated platform required?
  6. What vessels will you be working with? Overhead stirrers can be used with both flat-bottom vessels and closed reaction systems with round-bottom flasks.
  7. Does the device have a digital display for speed and torque, as well as a timer?
  8. What type of motor is used? Are the torque and speed specifications suited to your applications?

Choosing a Stirrer

The choice between a magnetic or overhead stirrer should be decided primarily by the viscosity of the sample and its scale. Overhead stirrers are useful when the sample’s viscosity may change significantly during the stirring process, or when viscosity poses a challenge in general. Magnetic stirrers offer easy usability and greater functionality, such as digital controls that display stirrer parameters.

Hotplate Stirrers

When selecting a hotplate stirrer, pay close attention to the interface. An easy-to-use interface will make the stirrer more enjoyable to use, easier to train with, and decrease errors. Additionally, since hotplate stirrers are used consistently—if not constantly, in some labs—look for a model that is known to be durable.