Overview of Microwave Digester

01 Feb.,2024

 

The Microwave digestion technology uses the permeability and activating reaction ability of microwaves to heat reagents and samples in a closed container, which can increase the pressure and reaction temperature in the sample preparation container, thereby greatly increasing the reaction rate and shortening the sample preparation time. That explains the existence of microwave digesters.

In order to prevent civil microwave power from interfering with radio communication, broadcasting, television, radar, etc., it is internationally regulated that the frequency of civilian microwaves for industry, scientific research, medical care, and households is 2,450 MHz. Therefore, the frequency used by the internationally universal microwave digesters is basically 2,450 MHz, while the industrial microwave digesters and household microwave ovens are basically within the Hertz range.

 

Substances related to microwaves

1. Substances that absorb microwaves

Substances with polar molecules will absorb microwaves (substances with a large loss coefficient), such as water and acid. The molecules have a dipole moment (that is, the centers of the positive and negative charges of the molecules do not coincide). In the microwave field, the polar molecules change directions rapidly along with the change of microwave frequency and rotate back and forth, thus colliding and rubbing against each other to absorb microwave energy and increase the temperature. The food we eat contains water, which is a strong polar molecule, so it can be heated in a microwave oven.

2. Substances that reflect microwaves

Metal materials, like copper, iron, aluminum, etc., do not absorb microwaves, but only reflect them. The hearth of a microwave oven is made of metal (stainless steel plate), reflecting back and forth on the heating material. Don't put a metal container into a microwave oven. The reflected microwave will damage the magnetron.

3. Substances that penetrate microwaves

The insulator can pass through microwaves and hardly absorb the energy of the microwaves, such as glass, ceramics, plastics (polyethylene, polystyrene), polytetrafluoroethylene, quartz and paper. They are transparent to microwaves, and microwaves can travel forward through them. Essentially, the absorption intensity of a substance to microwaves depends on the complex permittivity of the substance, so the larger the loss factor, the stronger the ability to absorb microwaves. Household microwave ovens are mainly made of plastic products.

 

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