A magnetic stirrer is a laboratory tool that uses a rotating magnetic field produced by a moving magnet or a stationary electromagnet to swiftly stir or mix a solution by spinning a stirrer bar submerged in a liquid.
The first magnetic stirrer was given a patent in 1917 by Utahn Richard Stringham. In the majority of contemporary magnetic stirrers, an electric motor rotates the magnets. A magnetic stirring system often includes a connected heating device for warming the liquid. With magnetic stirrers, small amounts of low viscosity may often be stirred. To prevent interference with the magnetic field, stirrers must be used with glass or another non-metallic beaker. It is perfect for stirring in several contexts, including academia, business, agriculture, healthcare, and homebrewing.
Table of Contents
- Principle of Magnetic Stirrer
- Parts of a Magnetic Stirrer
- Characteristics of Magnetic Stirrer
- Magnetic Stirrer operating procedure
- Types of Magnetic Stirrers
- Applications of Magnetic Stirrer
- Advantages of Magnetic Stirrer
- Limitations of Magnetic Stirrer
- Precautions
- Magnetic Stirrer Examples
Principle of Magnetic Stirrer
According to the laws of attraction for opposing charges and repulsion for similar charges, the magnetic stirrer works. Solvents with different viscosities are often stirred using the stirring speed, which is customizable. A stirring bar within the jar is rotated by a rotating magnetic field produced by a magnet powered by a micromotor, allowing a well mixed reaction to occur. It has a temperature control system that allows it to heat and adjust the sample's temperature in line with the needs of the experiment, making sure that the mixed liquid meets the criteria of the test while maintaining the needed temperature.
Parts of a Magnetic Stirrer
The two primary components of a magnetic stirrer are a stir bar and a hot plate stirrer. A hot plate stirrer machine may also have a stationary electromagnet, a heated plate, a temperature control knob, and a speed control knob.
Parts of a Magnetic Stirrer
Stir bar: The terms "stir bar" and "spin bar" refer to a small, white, rectangular, Teflon-coated magnet. These bars' is to shake solutions; nothing else. Together, they operate a stirring motor. The stir bar is placed in a container with liquid and then set over a stirring motor. When the stir motor is activated, the bar rotates and the liquid is stirred. The stir bar's form, which might be octagonal, circular, etc., is determined by the shape of the vessel and the viscosity of the stirring media. The stir bar is millimetres to a few centimetres in size.
Temperature controlling knob: The magnetic stirrer has a temperature control knob that regulates the temperature according to the volume, viscosity, and size of the vessel holding the liquid.
Stir bar retriever: These magnets have PTFE (teflon) rod permanently inserted. It makes it safer and simpler to remove magnetic stirring and spin bars from caustic and irritating liquid samples in glass flasks. It is, however, less frequently used in magnetic stirring.
Characteristics of Magnetic Stirrer
Capacity: Obviously, stirring seldom involves the use of flowing water. Because of this, the nominal capacity is far higher than the actual capacity. In the 3-liter capacity of the micro versions, a minimum of 1 litre of surfactant solution and about 250 ml of an emulsion may be accommodated.
Maximum permitted temperature and humidity: When working in a wet lab, a tropical environment, or when preparing to combine hot materials, one should consider the instrument's maximum permitted operating temperature and humidity.
Dimensions of the mounting surface: The surface area of each magnetic stirrer determines the size of beakers that may be used with it.
The magnet: Basic rods and various geometric forms like ellipses, discs, and others are among the many sizes and shapes of magnets that are available. The beaker must fit the stirring rod, which is normally 0.5–1.0 cm smaller in diameter than the beaker. Undoubtedly, using different magnetic rods while working with varied beaker sizes is necessary.
Magnetic Stirrer operating procedure
1. Prepare a container that already contains the liquid solution.
2. You should set the container on the hotplate.
3. To turn on the hotplate, connect to the mains.
4. You may change the hotplate's temperature by pushing the temperature setting button.
5. Put the magnetic stir bar in a solution-filled container.
6. To alter the magnetic stirrer's speed, turn the speed adjustment button anticlockwise. If the stirring speed is too high, turn the magnetic stirrer adjustment knob anticlockwise.
7. The liquid mixture should be stirred until homogeneity is attained.
8. Once finished, take the magnetic stirrer out of the liquid solution container.
9. In order to switch off the hotplate, disconnect from the mains.
10. To lift the container, use heated hands.
Types of Magnetic Stirrers
Magnetic stirrers can be categorised based on their size, design, and intended usage. Here are a few different kinds of magnetic stirrers:
Magnetic Mini Stirrer
The magnetic stirrers used in labs are small and take up little room. They contain electrical controls that let the user regulate the speed accurately. It is resistant to corrosive and harmful agents in the laboratory. The stirrer's rotations per minute (rpm) are controlled by the speed regulator.
Magnetic Stirrer with Timer
A magnetic stirrer with a timer allows the motor to be automatically shut off after a certain amount of time. When the predetermined amount of time has passed, a built-in timer will turn the stirrer off. The weight is automatically removed, and the speed is automatically reduced.
Heavy-Duty Magnetic Stirrer
The heavy-duty magnetic stirrers come with high mixing capabilities. Additionally, they are strong and have high chemical resistance. They could be the best tool the lab has to employ for accurate results. Heated magnetic stirrers are necessary for the majority of chemical processes.
Battery Powered Magnetic Stirrer
They can be used in locations without electricity or other challenging conditions. They run on batteries, are mostly used in incubators, and have rubber feet for stability. They are transportable and low in weight.
Air-operated Turbine Magnetic Stirrer
For mixing liquids up to 1 litre of solution, the air-operated turbine magnetic stirrer is the best appliance. This magnetic stirrer is powered by a low-pressure air supply. The fact that its magnetic stirrer minimises the possibility of sparking from electrical sources is a key advantage.
Applications of Magnetic Stirrer
- In chemistry labs, combining two or more components allows for the performance of chemical experiments and synthesis.
- In microbiology labs, it is used to produce a medium for the cultivation of microorganisms.
- It is employed in chemical and biology investigations to prepare samples and carry out analyses.
- It is used to reduce the consumption of organic solvents and obtain the highest extraction efficiency from plant material.
- Other applications need the blending of several liquid types to produce equal mixing, such as oil analysis, soil suspension, the production of buffer solutions, pH testing, etc.
Advantages of Magnetic Stirrer
- It makes it possible to mix reagents at a constant temperature.
- It prevents rapid boiling when the container is closed.
- Both the reaction and evaporation rates are increased.
- It might be used to finish lengthy treatments like protein dialysis.
- There is no danger of contamination since just a tiny magnet bar that can be readily washed and disinfected has to be inserted within the sample.
- They provide superior productivity and accuracy, are quiet, and are easier to operate than electronic stirrers.
- The stir bar revolves at various speeds and can stir up to one litre of liquid.
- The samples might be combined for a long time—possibly overnight.
- Since there are no exterior moving parts, there is no wear and tear.
- It is little and takes up very little room.
Limitations of Magnetic Stirrer
- Nanoparticle dispersion is not successful. Nanotubes are dispersed using magnetic stirring in conjunction with sonication.
- Magnetic stirrers struggle with thick suspensions or viscous liquids.
- Magnetic stirrers are only useful for relatively modest studies since stir bars come in a restricted size. (under 4 liters).
Precautions
- The instrument housing needs to be properly grounded in order to avoid accidents.
- The high-speed operation can operate continuously for four hours while the medium-speed operation can run constantly for eight hours without experiencing excessive vibration.
- Keep the instrument dry and clean, keep solutions out of it, switch off the power when not in use, and take other precautions to prevent damage.
- When not in use for a prolonged period of time, turn off the electricity and store the products in a dry, ventilated space.
- Stirring heating shouldn't take too long; little usage can prolong the life.
- To check that the location is accurate and the beaker's bottom is flat, slow down or switch off a stirrer if it is beating or not stirring during mixing.
Magnetic Stirrer Examples
Hotplate Magnetic Stirrer BS series (Biobase)
- Both stirring and heating can take place simultaneously.
- Power of stirring and heating is infinitely variable.
- 2000 rpm maximum speed and 380°C maximum temperature.
Mini Magnetic Stirrer (Thomas Scientific)
- It is lightweight and portable, and its compact footprint frees up valuable workbench space.
- By reducing lab noise, the tiny stirrer's quiet operation and minimum vibration let users concentrate.
- Ideal for routine stirring operations in lab settings for many types of research, including general research, life science, industrial, quality analysis, and clinical care.
Magnetic Stirrer JBQ-XJ-MS236 (Biometer)
- Its use is simple and useful.
- Variable experimental applications are supported by the knob operation, adjustable mixing speed, and uniform mixing.
- A large capacity built-in lithium battery offers a minimum battery life of 48 hours, making it useful for mobile use in many different sectors.
Magnetic laboratory stirrer Cimerac™ Basic (Thermo Scientific)
- Thermo Scientific's basic Cimarec stirrers are inexpensive and perfect for regular use.
- It can stir at speeds ranging from 100 to 2500 rpm.
- The stirrer has control knobs for precisely changing speed. Its updated top-plate design makes breakage less likely.
- The spillway's design also guards against interior damage from spills.
- In its in-built ring-stand holder, a support rod with a 1.3 cm diameter may be inserted.
Magnetic laboratory stirrer MST (VELP Scientifica)
- Strong, compact, and adaptable
- equipped with a brushless motor
- Excellent chemical resistance is guaranteed by techno-polymers.
- takes a flask up to five litres.
- Built to last as long as possible and covered by a three-year warranty
- Ideal for BOD, microbiology, biochemistry, microtitration, and it maintains its coolness even after hours of continuous usage.
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