first: decompression concentration by some of the components under test for heat is not stable, easy to decompose at high temperatures, with reduced pressure concentration, reduce the boiling point solvents, as well as rapid enrichment to the volume, and decomposition of analyses can be avoided.
Of reduced pressure concentration device for all glass vacuum concentrator, also known as the K - D concentrator, this instrument is a kind of commonly used vacuum distillation device, the method has the advantages of low concentration, low temperature, speed, losses and characteristics of easy to control the volume you need for the concentration of the analyses thermal unstable extract, especially suitable for analysis of pesticide residues in the sample solution concentration. In addition, it can also be used for the purification of the solvent distillation.
Second:flow air blowing and steamed method is to blow in air or nitrogen containing cleaning liquid in the container, falling liquid surface vapor pressure of the solvent to evaporate and reach the purpose of enrichment. This method is simple, but the efficiency is low, is mainly used for smaller, the solvent boiling point lower the concentration of the solution, but high vapor pressure of a component is easy to damage. For residue analysis, since most of the components under test is not so stable, as usually as purging with nitrogen gas. For heating in the hot bath to solvent evaporation, and should be controlled water bath temperature, the analyses to prevent oxidation decomposition or volatile, for the high vapor pressure of pesticides, the operation must be under 50%, the residual solution can only be removed moderate nitrogen flow at room temperature, lest cause the loss of pesticides.
Third, rotary evaporator concentration by rotary evaporator by electronic control, make the flask under the appropriate speed to increase the rotation evaporation area. Enrichment can be making through vacuum pump evaporation flask in a state of negative pressure. Dressed in the evaporation of the flasks extract, under the condition of heating in water bath or oil bath, because at the edge of the decompression under rotation, heating, to make the solution adhesion of evaporation inside the bottle wall forming a thin layer of liquid membrane, proliferation, increased evaporation area, and, because of the negative pressure, the boiling point of solvent is reduced, further improve the evaporation efficiency, at the same time, by evaporation of the solvent was condensed in the condenser, return to receive bottles.
As a result, the more average evaporation device efficiency exponentially, and can prevent the bumping and measured components of oxidation decomposition. Evaporation of the solvent was condensed in the condenser, the solvent backflow to the reception in a bottle; the solvent recovery is very convenient.
Rotary evaporation concentrator consists of mechanical parts, electric cabinet and glass apparatus composed of three parts. At present in the manufacturer of the rotary evaporator is more, various model. But it is not recommended. Because this method enrichment is slow, the operating trouble, especially not suitable for small samples.
Four, vacuum centrifuge enrichment centrifuge enrichment process is adopted by the vacuum centrifugal concentration meter, vacuum pumps and vacuum centrifugal condensed system composed of three parts. Through comprehensive use of centrifugal force, heat, and external vacuum pump with vacuum function for solvent evaporation, and can handle multiple samples at the same time and will not lead to cross contamination. And through ultra-low temperature cold trap capture solvent, cold trap is effective to capture most of the solvent steam for vacuum pump damage, provide effective protection for high vacuum pump. Solvent to evaporate quickly achieve the purpose of enrichment or dry sample. After centrifugal concentration of the sample， it can be easily used in all kinds of qualitative and quantitative analysis.
At present, the domestic the ZLS-2 vacuum centrifugal concentration meter is one of the best. The machine design is exquisite; the operation is simple, easy to use. Non-contact drive rotation system without maintenance. Many turned to supporting the use. Progress of the transparent cover plate, convenient for observation. Use TFT true color large touch screen LCD display, intelligent microprocessor control and simple operation interface directly. Drying chamber adopts aluminum alloy manufacturing and coating anticorrosive processing.