Microwave digestion usually refers to the acid dissolution of various samples in a closed container using microwave heating (open container microwave digestion is not discussed). The characteristics of closed container reactions and microwave heating determine its advantages of complete, fast, and low blank.
High pressure (up to 100-150 bar) and high temperature (usually 170-220°C) strong acid vapor bring psychological pressure on laboratory safety. The current commercial microwave digestion systems generally have temperature and pressure measurement and even temperature and pressure control technologies. Therefore, safety is well guaranteed. However, as potential users (or users), one should still understand some of its characteristics not only to choose the microwave digestion system but also for safer use.
1. The body should be a rectangular industrial resonant cavity enclosed by a metal wall.
2. The furnace door should be equipped with a triple-independent interlock sensing device, which cuts off the power when the furnace door is opened. The microwave device cannot work without the furnace door being closed.
According to the power emission mode, microwaves are divided into pulse and non-pulse. The traditional fixed power output characteristic is the switchable pulse microwave. This control mode is not only difficult to control but may also directly affect the digestion effect. The current microwave development direction is automatic power frequency conversion control and non-pulse technology. Its characteristic is automatic power change, and output is all non-pulse microwave. Its advantages are that it does not need to close the microwave emission, and under continuous microwave emission conditions, it automatically linearly changes the microwave power output based on temperature and pressure feedback signals, adjusts the reaction state, and controls the temperature more accurately to ensure safe and smooth experiments.
1. The microwave digestion instrument should be placed on a sturdy and stable table, with no obstructions on the top and sides of the furnace body and at least 5 cm of space, and the back wall should have at least 10 cm to ensure good ventilation.
2. It should be away from the heat source to avoid hot air and water vapor from entering the microwave oven and causing malfunctions. It should also be far away from the water source to avoid the danger of electric leakage caused by splashing water.
3. Do not place it close to strong magnetic materials or magnetic appliances because external magnetic fields can interfere with the uniform distribution of magnetic fields inside the furnace, reducing heating efficiency.
4. Other normal laboratory temperature and water and electricity conditions.
Do not directly use explosive nitrocellulose, TNT, hydrazine, ammonium perchlorate, flammable mixtures containing nitric acid and catechol, nitric acid and triethylamine mixtures, nitric acid and acetone mixtures, acetylene compounds, acrolein, ethylene glycol, propylene glycol, alkanes, ketones and other compounds in the digestion tank.