Magnetic Stirrer: Definition, Principle, Features, Advantages, Applications

A laboratory apparatus known as a magnetic stirrer is utilized to generate a rotating magnetic field, commonly employed for stirring and mixing solutions in a range of scientific contexts including chemistry, biology, and biochemistry. In other words, it is a type of lab instrument that efficiently mixes and stirs solutions by spinning a stir bar submerged in a liquid using a revolving magnetic field.

Magnetic Stirrer Definition, Principle, Features, Advantages, Applications
Magnetic Stirrer Definition, Principle, Features, Advantages, Applications

Applications for magnetic stirrers can be found in many areas, including biology, chemistry, business, academia, homebrewing, and agriculture. When used in conjunction with other conventional stirring techniques like stirring rods or overhead stirrers, they provide a practical and effective way to stir small amounts of low-viscosity liquids.

What is a magnetic stirrer?

A laboratory tool extensively employed is the magnetic stirrer, alternatively termed a magnetic mixer, which has significantly transformed the stirring and mixing of solutions in scientific settings. Its operation relies on the creation of a rotating magnetic field, achieved through a rotating magnet or stationary electromagnets. This magnetic field induces rapid spinning of a stir bar submerged in a liquid, streamlining the mixing procedure.

  • The simplicity of sterilization and cleaning is one benefit of using magnetic stirrers. Unlike other stirring devices, which may be more difficult to handle, stir bars can be simply removed from the liquid, enabling full cleaning and disinfection. This functionality is very useful in scientific environments where sterility and cleanliness are essential.
  • Magnetic stirrers are frequently used with glass or other non-metallic beakers to ensure compatibility with the magnetic field. Fleas, another name for stir bars, are usually covered with glass or PTFE to stop any chemical interactions with the substance being stirred. This coating makes sure the stir bar doesn’t contaminate the solution and stays inert.
  • Overall, due to their ease of use, effectiveness, and diversity in stirring and mixing applications, magnetic stirrers have become essential instruments in many laboratories. They are now an essential component of scientific research and experimentation, helping to develop numerous fields of study through their constant evolution and improvements.

Principle of magnetic stirrer

  • The magnetic stirrer operates based on the fundamental characteristics of magnetic fields, leveraging the attraction between opposite charges and the repulsion between like charges.
  • This device facilitates the stirring and mixing of solutions by employing a micromotor-driven magnet to generate a rotating magnetic field.
  • Within the apparatus, a stir bar or flea immersed in the liquid undergoes rapid spinning induced by this magnetic field.
  • The stirring speed is adjustable to meet experimental requirements.
  • The rotational motion of the stir bar, prompted by the magnet’s magnetic field, creates turbulence, ensuring thorough mixing and uniform distribution of components in the liquid.
  • Many magnetic stirrers also feature a temperature control system, allowing for the regulation of sample temperature during stirring.
  • This capability ensures that the mixed liquid remains at the required temperature for specific experiments, enhancing its effectiveness in various laboratory applications.
  • In summary, the magnetic stirrer principle exploits magnetic fields to induce rotational motion in a stir bar, promoting efficient mixing and stirring of solutions, with the added versatility of temperature control for precise experimental conditions.

Features of magnetic stirrer

Magnetic stirrers have several properties that add to their usefulness and adaptability. The following are some essential characteristics of magnetic stirrers:

  • A magnetic stirrer’s capacity is the largest amount of liquid it can hold while swirling. When selecting a magnetic stirrer, it is important to take the real capacity into account, even if the nominal capacity is typically higher.
  • A magnetic stirrer’s maximum speed is expressed in revolutions per minute (rpm). The majority of magnetic stirrers can mix effectively because of their speed range, which is roughly 1000 rpm. High-performance models, on the other hand, have stronger stirring capabilities due to their ability to reach speeds of up to 2500 rpm.
  • A magnetic stirrer’s maximum permitted operating temperature and humidity should be taken into account, particularly when working with hot materials, in tropical climates, or in wet lab conditions. Verifying these specs guarantees the stirrer can function flawlessly under the appropriate conditions.
  • The appropriate beaker sizes for use with a magnetic stirrer depend on the size of its mounting surface. To make sure the stirrer can securely hold the specified beaker size, the surface area should be taken into account.
  • Magnetic stirrers make use of a range of magnet sizes and forms, including rods and geometric forms like discs and ellipses. To guarantee compatibility, the stirring rod magnet’s size should be marginally less (usually 0.5–1.0 cm) than the beaker’s diameter. For varying beaker sizes, different magnetic stir bars might be needed to get the best-stirring results.

Parts of magnetic stirrer

parts of magnetic stirrer
  • Hot Plate: Usually composed of ceramic or stainless steel, the top plate is also referred to as the hot plate. Ceramic top plates have a strong chemical resistance, making them ideal for working with caustic chemicals and for jobs like titrations that call for clear color vision. Unlike aluminum, stainless steel top plates produce no eddy currents and offer a robust coupling and stirring action.
  • Stir bar: The stir bar, also known as a spin bar, is a tiny magnet with a non-reactive material coating, such as Teflon. Its primary function is to stir solutions when they are placed on top of a magnetic stirrer in a container filled with liquid. The vessel shape and the viscosity of the stirring media determine the shape of the stir bar, which might be circular or octagonal. Stir bars are available in a range of sizes, from millimeters to centimeters.
  • Stationary Electromagnet: A magnetic field is produced by the stationary electromagnet, which is located inside the magnetic stirrer. When the stir bar is immersed in the liquid, this magnetic field causes it to rotate, causing a high-speed stirring action that homogenizes the mixture.
  • Speed Controlling Knob: The stir bar’s rotational speed, which is expressed in revolutions per minute (rpm), can be changed by the user using the speed control knob. Depending on the liquid’s density or the particular needs of the project, the speed can be changed.
  • Temperature Controlling Knob: Numerous magnetic stirrers have a knob to adjust the temperature. The temperature of the liquid being churned can be controlled and adjusted by the user using this knob. The volume, viscosity of the liquid, and size of the vessel are some of the variables that affect temperature control.
  • Stir Bar Retriever: A stir bar retriever is a device that has a magnet permanently inserted in a PTFE (Teflon) rod, albeit it is less frequently employed in magnetic stirring. It makes the safe and simple extraction of magnetic stir bars from caustic and irritating liquid samples in glass flasks possible.

Operating procedure of magnetic stirrer

  • Ensure that the needed liquid solution has previously been made and placed in an appropriate container or jar.
  • Place the container securely on the top plate or hotplate of the magnetic stirrer. Make sure it’s centered and stable.
  • Connect the magnetic stirrer to a power source to provide electricity to the gadget.
  • Press the temperature setting button or knob on the magnetic stirrer to modify and establish the desired temperature for heating the solution, if necessary. To precisely set the temperature, follow the instructions provided with the specific model.
  • Carefully insert the magnetic stir bar into the liquid-filled vessel. Make sure the stir bar is completely submerged in the solution and appropriately positioned for optimum stirring.
  • To control the magnetic stirrer’s stirring speed, use the speed adjustment button or knob. Rotate the adjustment knob clockwise to increase speed and counterclockwise to decrease it. Adjust the speed based on the desired mixing intensity.
  • Turn on the magnetic stirrer and let it swirl the liquid mixture. Continue stirring until the required homogeneity is obtained, making sure that all ingredients are well incorporated.
  • Once the stirring operation is complete, carefully lift and remove the magnetic stirrer from the container, taking care not to spill or splash the liquid solution.
  • Unplug the magnetic stirrer from the power source to ensure its safety.
  • Lift and handle the container using suitable protective protection, such as hot hands or heat-resistant gloves, as it may be hot from the magnetic stirrer’s action.

Types of magnetic stirrers

  • Mini magnetic stirrers: Mini stirrers are compact, take up little room, run quietly, and have low vibration, making them simple to use. It is resistant to hazardous and caustic laboratory chemicals. You can also adjust the speed to ensure that it does not exceed the maximum. These microscopic magnetic stirrers are used in laboratories and need less room due to their small size. This stirrer is insensitive to the presence of corrosive chemicals in the laboratory.
  • Magnetic Stirrer with Timer: This stirrer has a built-in timer that allows us to regulate the established parameters for a defined amount of time, as the name implies. Ezoic When the timeout period expires, the rotations halt automatically. These stirrers are useful if you want the motor to shut down on its own.
  • Heavy Duty Magnetic Stirrer: The Heavy Duty Magnetic Stirrer is chemically resistant and has a large mixing capacity. The Heavy Duty Magnetic Stirrer may be an excellent choice for both laboratory and industrial applications. Ezoic With a large mixing capacity, these stirrers could be one of the greatest solutions for attaining good results. They are also chemically and physically durable.
  • Battery-operated Magnetic Stirrer: When electricity is unavailable, battery-powered magnetic stirrers are ideal for use in the field, incubators, and other environments. They’re also portable and lightweight. These battery-powered magnetic stirrers might be beneficial in regions where the power supply is weak or fluctuates. Rubber feet are given to help with stability.
  • Air-Operated Turbine Magnetic Stirrer: Air turbine magnetic stirrers use low-pressure air to generate magnetic stirrer rotations. Ideal for use in areas with potentially hazardous solvent vapors. The Air Operated Turbine Magnetic Stirrer is capable of stirring up to 1 litre of solution.

Test requirements of magnetic stirrer

Magnetic stirrers don’t require any particular testing, yet there are a few general things to keep in mind when using them:

  • Selection of the appropriate stir bar: The size, form, and speed of the stirrer should all be taken into consideration while selecting the stir bar.
  • Calibration of the stirring speed: To ensure precise and reliable results, the magnetic stirrer’s speed should be calibrated using a tachometer or a comparable device.
  • Compatibility of materials: The appropriate substances that are compatible with the chemical or biological sample being mixed should be utilized with magnetic stirrers.
  • Avoiding magnetic interference: Speakers, motors, and other magnetic items that could interfere with the magnetic field and reduce the stirring efficiency should be kept well away from magnetic stirrers.
  • Safety considerations: When handling dangerous or poisonous compounds, magnetic stirrers should be used with the appropriate safety precautions, such as the use of protective glasses, gloves, and other safety gear.
  • Maintenance: To ensure consistent performance and avoid contamination, it is imperative to undertake routine cleaning and maintenance on the magnetic stirrer, stir bar, and the vessel being stirred.

Applications of magnetic stirrer

  • In chemical laboratories, magnetic stirrers are widely used for mixing and agitating different components during synthesis and experimentation. They ensure homogenous outcomes and enhanced reaction kinetics by offering efficient and uniform mixing.
  • Magnetic stirrers are used in microbiology labs to make culture media for microbe growth. They aid in distributing chemicals and nutrients evenly, creating the ideal environment for microbial development.
  • When it comes to getting samples ready for analysis in chemical and biology studies, magnetic stirrers are essential. They help dissolve and combine reagents, ensuring that samples are ready for further examination methods including titration, chromatography, and spectroscopy.
  • In oil analysis labs, magnetic stirrers are used to combine oil samples with different solvents or reagents before analysis. As a result, it is easier to measure the oil’s viscosity, density, and pollutants.
  • In extraction procedures, magnetic stirrers are used, especially for extracting plant materials. Magnetic stirrers improve extraction effectiveness and lower solvent usage by continually swirling the mixture of plant material and organic solvents, which results in a more effective extraction of desired chemicals.
  • In addition to its use in soil suspension, buffer solution production, pH determination, and general mixing duties, magnetic stirrers are found in numerous additional applications. When blending different liquids to produce homogeneity and uniform mixing, they are especially helpful.

Advantages of magnetic stirrer

  • It is possible to avoid the formation of strong boiling in a sealed container by using magnetic stirring. This aids in keeping the mixing environment steady and under control.
  • Magnetic stirrers improve the speed of evaporation and reaction by providing constant stirring. This is advantageous for procedures that call for rapid evaporation and effective mixing, which reduce reaction times.
  • Reagents can be mixed at a consistent temperature with the use of magnetic stirrers. They may have a heating element installed, which would allow for simultaneous stirring and heating. This is especially helpful for procedures and investigations that call for exact temperature control.
  • Protein dialysis and other lengthy processes requiring constant mixing of samples over long periods are ideal applications for magnetic stirrers. The stirrer’s capacity to run for hours or even overnight ensures that the intended results are obtained.
  • In the laboratory, magnetic stirrers provide exceptional accuracy and productivity. Their operation is simple, effective, and silent. Magnetic stirrers are dependable, long-lasting, and require less maintenance than electronic stirrers.
  • With magnetic stirrers, the sample is only partially immersed in a tiny magnet bar that is frequently coated with glass or PTFE. This lowers the possibility of contamination by removing the possibility of extraneous moving parts coming into touch with the sample.
  • With the ability to mix up to one liter of liquid, magnetic stirrers are capable of handling bigger amounts. Because of their adjustable speed control feature, users can tailor the stir bar’s rotational speed to meet their own needs. Magnetic stirrers take up very little room in a laboratory setup thanks to their small size. The instrument has a longer lifespan since there are fewer moving external elements, which reduces the chance of wear or breakage.

Limitations of magnetic stirrer

  • In general, magnetic stirrers work well for modest-scale investigations. The amount of liquid that can be efficiently stirred is restricted by the size of the stir bars. Magnetic stirrers are often advised for research involving less than four liters. It might be necessary to use different stirring techniques for larger-scale research.
  • Nanoparticles cannot be effectively dispersed using magnetic stirrers. To accomplish a proper dispersion of nanotubes and other nanoparticles, sonication-coupled magnetic stirring—a technique that combines the application of ultrasonic waves with magnetic stirring—is frequently employed for this purpose.
  • Using magnetic stirrers to stir viscous liquids or thick suspensions can be challenging. It’s possible that the magnetic field’s rotation won’t exert enough force to sufficiently combine very viscous materials. Other stirring techniques, including mechanical agitators or overhead stirrers, might be more appropriate in some situations.

Calibration of magnetic stirrer

  • Start the calibration process with a thermometer calibrated to 300°C. This assures that, during the calibration process, the temperature readings are accurate.
  • Place the beaker or flask with the calibration sample in the magnetic stirrer’s center of the heating plate.
  • In order to start the magnetic stirrer, press the ON button. A magnetic stirrer or stir bar should not be used during this calibration process.
  • The magnetic stirrer’s temperature can be changed by turning the temperature knob or by using the temperature control feature.
  • Make sure the calibrated thermometer is completely immersed in the calibration sample by inserting it into one side of the beaker.
  • Observe the temperature reading on the calibrated thermometer in addition to noting the temperature on the magnetic stirrer’s control panel.
  • Repeat the procedure by varying the magnetic stirrer’s temperature setting and noting both the temperature on the display and the temperature on the calibrated thermometer. Always remember to monitor and compare the readings.

References

  • Jin, C., Zhou, W., Luo, D., Huang, Y., Wang, M. and Zhang, L., 2019. Automatic control of magnetic stirrer using webcam as the feedback sensor. Review of Scientific Instruments, 90(5), p.055109.
  • Pavan, P.C., Tambe, S.S. and Kadam, S.S., 2012. Design and development of digital magnetic stirrer with temperature controller. International Journal of Engineering Research and Applications, 2(3), pp.1520-1526.
  • https://universe84a.com/magnetic-stirrer-introduction-principle/
  • https://microbiologynote.com/magnetic-stirrer-definition-principle-types-parts-uses/
  • https://www.alphapedia.net/magnetic-stirrer/
  • https://www.biolabscientific.com/News/Role-of-Magnetic-Stirrer-to-Conduct-Biological-and-Chemical-Experiments

About Author

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Kabita Sharma

Kabita Sharma is a graduate student from the central department of chemistry, Tribhuvan University. She has been actively involved in research related to natural products, computational chemistry, and nanochemistry. She is currently working on enzyme assay, molecular docking, and molecular dynamic simulation.

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