Microwave is an electromagnetic wave with a frequency range of 300-300,000 MHz. The microwave frequency used by the microwave digester is the same as that of household microwave ovens, which is 2450 MHz. Systems containing water or acid are polar. Under the action of microwave electric field, the positive and negative directions are continuously changed at a rate of 2.45 billion times per second, causing molecules to collide and rub at a high speed to generate high heat. At the same time, in the microwave electric field Under the action of, the ions in the solution system flow in a directional direction to form an ionic current. During the flow of the ions, the ions rub and collide with surrounding molecules and ions at high speed, turning the microwave energy into heat energy.
Characteristics of microwave:
Straight line propagation and reflection characteristics of conductors (such as metals, etc.);
Penetrable insulator characteristics, such as plastic will not be heated;
Absorbency of substances containing medium molecules, that is, polar liquids will be heated;
Can be effectively uniform metal gap, uniform metal mesh shielding characteristics.
Microwave digestion mainly uses the advantages and characteristics of microwave heating. After adding acid to the sample to be digested in the special plastic digestion tank, a strong polar solution is formed. The heating property of the microwave body is used to heat the inside and outside of the solution at the same time. The heating is faster, more uniform, and improved. effectiveness.
In addition, microwave digestion is generally carried out in a closed high-pressure digestion tank. The pressure system can produce overheating (in short, it can be heated to a higher boiling point than normal pressure), which greatly improves the digestion speed and can digest the general wet digestion. Samples that cannot be digested.
Microwave digestion in a closed system can also prevent the loss of volatile elements, and carry out some items that cannot be performed by conventional wet digestion.
