Mechanism and characteristics of extraction in microwave vacuum drying oven

Microwave vacuum drying oven extraction, namely microwave-assisted extraction (MAE), selectively heats some regions of the matrix material or some components of the extraction system according to the different microwave absorption capabilities of different substances, so that the extracted substances are different from the matrix or system.
separation, so the dielectric constant is small, and the microwave absorption ability is relatively poor
.

1.
The mechanism of microwave vacuum drying oven extraction
.

Microwaves are electromagnetic waves with frequencies between 300 MHz and 300 GHz
.

It has four basic characteristics: volatility, high frequency, thermal characteristics and non-thermal characteristics
.

The commonly used microwave vacuum drying oven frequency is 2450MHZ
.

Microwave heating is the use of polar molecules (H2O, CH2Cl2, etc.

)
to rapidly rotate and align in a microwave electromagnetic field, resulting in tearing and friction heating
.

The heat transfer formula of the traditional heating method is heat source→container→sample, so the energy transfer efficiency is limited
.

Microwave heating is directly used to heat substances, and the method is heat source→sample→ware
.

The air container basically does not absorb and reflect microwaves, which fundamentally ensures the rapid transmission and full utilization of energy
.

 　　2.
The characteristics of microwave vacuum drying oven extraction
.

 　　①Reflected in the selectivity of microwave, due to the selective heating of polar molecules, the selectivity is dissolved
.

 　　②Microwave-assisted extraction greatly reduces the extraction time and improves the extraction speed
.

The traditional method takes several hours to a dozen hours, the ultrasonic method also takes half an hour to an hour, and the microwave extraction only takes a few seconds to a few minutes, and the extraction speed is increased by tens to hundreds or even thousands of times
.

 　　③ Microwave vacuum drying oven extraction is less limited by solvent affinity, more solvents can be selected, and the amount of solvent is reduced
.

In addition, microwave extraction is safe, reliable, non-polluting, suitable for large-scale production, and belongs to green engineering
.

The production line has a simple structure and can save investment
.

 　　Microwave extraction is generally suitable for thermally stable substances
.

For heat-sensitive substances, materials that are easily denatured or deactivated by microwave heating, good water absorption is required
.

Otherwise, it is difficult for cells to absorb enough microwaves to self-destruct, and microwave extraction has poor selectivity for components
.