Microwave is a kind of electromagnetic wave, which is an electromagnetic wave with a frequency of 300MHz to 300GHz, that is, an electromagnetic wave with a wavelength in the range of 100cm to 1mm, which means that the wavelength is between the far infrared and radio waves. In the microwave band, the wavelength band of 1 to 25cm is specially used for radar, and the rest is used for telecommunication transmission. In order to prevent civil microwave power from causing interference to radio communication, radio, television and radar, the frequency of civil microwave in industry, scientific research, medicine and household use is 2450 ± 50MHz internationally. Therefore, the frequency used by microwave digester from professional microwave digester manufacturers is basically 2450MHz, and the same is true for household microwave ovens.
(1) Metal materials do not absorb microwaves, but only reflect microwaves, such as copper, iron, aluminum and so on. Use metal (stainless steel plate) as the hearth of the microwave oven, and the back and forth reflection acts on the heating material. Metal containers cannot be used in microwave ovens, as reflected microwaves can damage the magnetron.
(2) The insulator can transmit microwaves, and it hardly absorbs the energy of microwaves, such as glass, ceramics, plastics (polyethylene, polystyrene), teflon, quartz, paper, etc., which are transparent to microwaves, and microwaves can penetrate them to transmit forward. None of these substances absorb microwave energy, or absorb very little microwaves. The strength of a substance to absorb microwaves is essentially related to the complex permittivity of the substance, that is, the greater the loss factor, the stronger the ability to absorb microwaves. Most household microwave containers are plastic products. The materials used in the microwave airtight digestion and dissolving tank are polytetrafluoroethylene, engineering plastics, etc.
(3) Substances with polar molecules will absorb microwaves (substances with a large loss factor), such as water, acid, etc. Their molecules have permanent dipole moments (ie, the centers of positive and negative charges of the molecules do not coincide). In the microwave field, the polar molecules change their orientations rapidly with the frequency of the microwaves and rotate back and forth, causing the molecules to collide and rub with each other, absorbing the energy of the microwaves and increasing the temperature. The food we eat contains water, and water is a highly polar molecule, so it can be heated in a microwave.
The microwave digester can perform rapid and efficient digestion and determination of chemical oxygen demand (CODcr), total phosphorus (TP), and total nitrogen (TN) in various surface water, domestic sewage, and industrial wastewater.
Microwave digestion system is widely used in the identification and management of water quality by environmental protection departments at all levels, water resources management departments and public health departments.
Microwave organic synthesis will replace traditional synthesis methods with its absolute application advantages. For example, the sample preparation with analytical instruments such as atomic absorption spectrometer, atomic fluorescence spectrometer, inductively coupled plasma emission spectrometer, inductively coupled plasma mass spectrometer, high performance liquid chromatography, gas chromatograph, etc. More and more laboratories have adopted imd kol microwave sample processing systems to replace other time-consuming, labor-intensive, and polluting methods.