How to choose the appropriate magnetic stirrer for a heating magnetic stirrer?
Laboratory Guide | Tengyi Technology
The heated magnetic stirrer is one of the commonly used equipment in the laboratory. It is mainly used to stir or simultaneously heat and stir low-viscosity liquids or solid-liquid mixtures.
Its important component - the magnetic stirrer (also called the rotor), achieves uniform stirring of the liquid through the action of the magnetic field.
Often laboratory users do not understand the types of stirrers, leading to improper selection and various problems such as rotor skipping.
This article will introduce in detail the basic principles, classification and factors that need to be considered when selecting magnetic stirrers, and provide you with a complete guide for selecting magnetic stirrers!
Working principle of magnetic stirrer
Place the container of liquid to be stirred with the stirrer in it on the base of the magnetic stirrer. When the motor of the magnetic stirrer works, a rotating magnetic field is generated near the base to drive the stirrer into circular motion, causing the liquid in the container to move in a circular motion. Form a vortex to stir the liquid. The advantage of the magnetic stirrer rotor is that it is simple to operate and does not produce sparks. It is widely used in chemistry, biology, medicine and other fields.
01 Classification of magnetic stirrers
According to material:
The material of the stirrer determines its corrosion resistance and scope of application. Common materials include glass, polytetrafluoroethylene, etc.
• Glass magnetic stirrer: The permanent magnet is sealed with high temperature resistant glass, suitable for stirring under high temperature conditions, and has excellent corrosion resistance and stability.
• PTFE magnetic stirrer: with a PTFE shell and a permanent magnet inside, it is suitable for most conventional stirring needs, but it should be noted that its melting point is low and should not be used at high temperatures (such as 300°C and above) Environment for long time use to prevent melting.
According to shape:
Magnetic stirrers come in various shapes, and each shape has its specific application scenarios and advantages.
The following are several common magnetic stirrer shapes and their applications:
1. Olive-shaped (Type A)
It is suitable for round-bottomed beakers and can effectively stir in round-bottomed containers to prevent the magnetic stirrer from moving closer to the center of the stirrer to ensure the stirring effect.
2. Cylindrical type with collar (Type B)
It is suitable for flat-bottomed containers and can provide stable stirring effect. It is suitable for all kinds of flat-bottomed containers.
3. Long column type without collar (type C)
It is suitable for flat-bottomed cylindrical beakers with low concentrations and can achieve effective mixing under low-speed rotation.
4. Cross shape
Achieves significant turbulence even at low speed rotation, suitable for low-speed stirring in biological applications, and can effectively stir sediment and bubbles at the bottom of the container.
In addition, there are also single-fin type, double-fin type, octagonal and other magnetic stirrers, each with different uses~
02 Factors to consider when choosing a magnetic stirrer stirrer
1. Shape of experimental container
Generally speaking, the smaller the contact area between the stirrer and the bottom of the container, the better, because the friction between the stirrer and the container is small, but the stirrer itself is required to have a high degree of balance; a large contact area is good for stability, so a balance between the two must be considered. Therefore, round-bottomed containers should use type A (olive-shaped) stirrers. For flat-bottomed containers, olive-shaped stirrers should not be used. Instead, use B-type stirrers. Type C (polygonal, cylindrical) magnetic stirrers are suitable for use in flat-bottomed cylindrical beakers with low concentrations.
2. Size of experimental container
The external dimensions of stirrers are large and small, so when purchasing, you should also choose based on the size of the bottom of the volumetric flask: if the capacity is within 1000mL, use a stirrer with a length of 15mm. When the capacity is within 3000mL, use a stirrer with a length of 300mm.
3. Liquid viscosity
If the viscosity of the liquid is grease-like, use a strong magnetic stirrer.
4. Stirring amount
When choosing a magnetic stirrer, you should also check the stirrer's maximum stirring capacity. Small magnetic stirrers use a small magnetic stirrer, while large-capacity magnetic stirrers use a longer magnetic stirrer. If a small magnetic stirrer uses a large-capacity magnetic stirrer, there is a possibility of burning the magnetic stirrer due to excessive load.
03 Storage and replacement of magnetic stirrer
Due to the magnetic material in the stirrer, it should be placed away from iron substances and other magnetic materials to avoid affecting the magnetism of the stirrer, causing magnetic attenuation and affecting its performance. Temperature, magnetic field and ferrous materials will all affect the residual magnetism of the magnetic stirrer, thereby affecting the stirring effect of the magnetic stirrer. Therefore, it is recommended to replace the magnetic stirrer promptly and regularly.
As an accessory, the stir bar is inseparable from the (heating) magnetic stirrer. As the more core heating magnetic stirring, its choice is even more important!
04 Select the appropriate (heated) magnetic stirrer
1 Accurate and stable
Prefer digital display (heating) magnetic stirrer to ensure accurate and stable temperature and stirring.
2 Temperature range and uniformity
Select the temperature range according to your needs to ensure uniform temperature distribution on the heating plate.
3 Stirring performance and sample viscosity
High-viscosity samples require a high-power mixer with excellent mixing performance.
4 safety performance
The equipment needs to have multiple safety features such as overflow prevention and overheating protection.
5. Easy to use and maintain
You should choose equipment that is easy to operate, has a friendly interface, and is easy to maintain.
6 sample capacity
Choose a small or large magnetic stirrer according to the experimental volume to adapt to the experimental needs of different sample capacities.
VELP, as a professional laboratory instrument manufacturer, here are several recommendations for (heating) magnetic stirrers that perform well on the market!!
▶ Heated magnetic stirrer AREX 5 Digital
https://www.te-lab-equipment.com.tw/arex-5-hot-plate-stirrer-arex-5.html
▶ Multi-point heating magnetic stirrer (6 points/15 points)
https://www.te-lab-equipment.com.tw/multi-hs-series-6-15.html
▶ Magnetic stirrer MSL 50 Digital
https://www.te-lab-equipment.com.tw/large-capacity-magnetic-stirrer-msl.html
▶ Digital multi-point heating mixer AM 4 Digital
https://www.te-lab-equipment.com.tw/am-4-digital-am4.html
Choosing the appropriate magnetic stirrer and magnetic stirrer is crucial to the success of the experiment. By comprehensively considering the experimental requirements, stirrer type, magnetic stirrer performance and brand advantages, the smooth progress of the experimental process and the accuracy of the experimental results can be ensured.