Magnetic Stirrer: Working Principle and Uses

Agitation and stirring processes are used in all the chemical and biological laboratories in various shapes and sizes. Irrespective of the specific application or process that is being performed, the researchers or technicians need to use the best laboratory equipment for the job to make sure the results are consistent. The wrong agitation process leads to inaccurate results; that's why it is very much crucial to understand agitation options as per the application. For the agitation, various options are available. Among them, magnetic stirrer hot plates, and overhead stirrers are widely used.

What is a magnetic stirrer?

Magnetic stirrers use a rotating magnetic field to move a stir bar around in liquid samples, and some are coupled with stirring hot plate. The movement of this stir bar mixes the samples thoroughly with rapid movement and agitation. The user controls the magnetic field's speed, so it can be customized to the specific sample that's being stirred. These stirrers should be used with glass or other non-metal beakers to prevent interference with the magnetic field.

Figure-1: Magnetic Stirrer and magnetic bead

How does it work?

A stir bar magnet is placed inside a container, immersed in the fluid. A separate magnet is placed underneath the container so that it attracts to the stir bar magnet. The lower magnet is usually attached to a motor that spins it. If the magnets are close enough, the stir bar magnet spins inside the container.

Depending on the application, you can configure your magnetic stirrer with hot plates to heat your samples as they are stirred. With the use of a hot plate stirrer, you can mix a wide variety of samples for different applications.

Magnetic Stirrers vs Overhead Stirrers

Aside from magnetic stirrers, the samples can be mixed using motor power overhead stirrers. The overhead stirrers can handle larger volumes of liquid samples and/or high viscous liquids. Magnetic stirrers, on the other hand, can mix samples in a sealed container and samples can be heated more evenly by magnetic stirrer hot plates.

Types of Magnetic Stirrers

The magnetic stirrers are classified according to the size, configuration and applications. The digital hotplate stirrers are available to monitor the temperature and rotations per minute (RPM) accurately. The best magnetic stirrer hot plate should be able to mix the viscus solutions efficiently and should not uncouple the bar from drive magnet.

Magnetic Mini Stirrer

The laboratory magnetic stirrers are compact and occupy less space in the laboratory, consist of electronic controls that allow the user to regulate the speed with greater precision. It is resistive to hazardous and corrosive chemicals in the lab. The speed regulator in the stirrer controls the RPM.

Figure-2: Mini magnetic Stirrer with the heating probe.

Magnetic Stirrer with Timer

Magnetic stirrer with timer helps to automatically shut off the motor after the specific period. An in-built timer will off the stirrer once the pre-selected period has completed.

Heavy-Duty Magnetic Stirrers

The heavy-duty magnetic stirrers come with high mixing capacity. They also have good chemical resistance and are highly durable. They can be the best choice instrument for the laboratory to achieve accurate results. The heating magnetic stirrers are essential for most of the chemical reactions.

Battery Powered Magnetic Stirrer

They can be used where there are no electric supply or other sensitive areas. They work with batteries, and are mostly used in incubators and consist of rubber feet for stabilization.

Air Operated Turbine Magnetic Stirrer

Air operated turbine magnetic stirrer is a perfect instrument for mixing liquid up to 1 litre of solution. It uses a low-pressure air supply to power this magnetic stirrer. The critical aspect of this magnetic stirrer is that it eradicates the sparking hazard from electrical sources.

Figure-3: Magnetic Stirrer with six stirring positions

Uses of Magnetic Stirrers

The primary use of magnetic stirrer or hot plate with magnetic stirrer is to conduct biological and chemical experiments by mixing two components. It is equally suitable for solids or liquid samples to obtain a consistent liquid mixture. Examples include media for bacterial growth and chemical synthesis.