The main factor of influence
Digestion temperature and pressure. The digestion temperature directly determines the digestion effect, and the pressure ensures the safety of the reaction.
How long does it take to digest a batch of samples? How can it be considered complete digestion?
A fully digested sample should be a clear transparent solution. Routine samples generally digest plus cooling time is 1 hour.
Does the microwave digester have to be used in a fume hood?
No. The microwave digestion instrument has its own exhaust system, you only need to put the exhaust pipe into the fume hood. The internal environment of the fume hood is not friendly to the microwave digestion instrument.
Can organic samples and inorganic samples be mixed in a microwave digestion instrument?
cannot. Organic samples react quickly, which will affect the digestion results of inorganic samples.
What are the requirements of the microwave digestion instrument for the sample form?
(1) Smash solid samples as much as possible, especially metals. If a metal block enters the microwave, it is easy to spark.
(2) The smaller the particle size of the sample, the larger the specific surface area in contact with the acid solution, and the better the digestion effect.
Which samples cannot be digested by microwave?
Pyrophoric and flammable compounds, aviation fuels (Jp-1, etc.), acetylene compounds, acrolein, alkenes, alkynes, liquid paints, coatings, pyrophoric mixtures (nitric acid and phenol, nitric acid and ethylamine, nitric acid and acetone, etc.), propulsion Agents (hydrazine, ammonium perchlorate, etc.), glycols (ethylene glycol, propylene glycol, etc.), perchlorates (ammonia perchloric acid, potassium perchlorate, etc.), ethers (fiber optic solution – ethylene glycol phenyl ether ), hydrocarbon-alkyl (butane, hexane, etc.), ketones (acetone, methyl ethyl ketone, etc.)
What are the commonly used reagents for microwave digestion of samples?
Commonly used reagents: nitric acid, hydrogen peroxide, reverse aqua regia, hydrochloric acid, HF, aqua regia, etc.
Nitric acid: the most commonly used acid in sample digestion. It is a strong oxidizing agent with a relatively low boiling point (120°C). Nitric acid has an ideal reaction ability under microwave power, and quickly produces reddish-brown gas formed by nitrogen oxides. Can destroy complex organic matrices.
Hydrofluoric acid HF: It is an effective solvent for dissolving silicon-based materials. Mainly mixed with nitric acid.
Hydrochloric acid: It is an ideal solvent for some metal oxides and metals that are more easily oxidized than hydrogen.
After adding the reagents, can it be put into the jar for microwave digestion immediately?
First observe whether the sample reacts violently after contact with the reagent. After shaking and mixing, if there is a violent reaction, the sealing cap should be closed after the reaction has basically disappeared. After shaking and mixing, if there is no reaction, it can be digested in a microwave.
How to clean the outer frame and other parts?
The frame, outer sleeve, and top pad cannot soak the acid tank. If you need to clean it, you can use a soft cloth dampened with clean water, wring it out, wipe it, and then dry it naturally. The lining must be cleaned and dried after each experiment. Ensure that the frame, outer sleeve, top pad, and inner lining are dry and free of sticky stains when microwave digestion is performed.
What is the drying temperature requirement of microwave digestion vessels?
The digestion vessels are generally dried in an oven with the temperature set at 120°C.
The microwave digestion vessels turn yellow after a period of use, how to deal with them?
After the digestion vessels have been used for a period of time, they turn yellow because nitrogen oxide gas is attached to the liner wall. It can be baked in an oven at a temperature of 180°C for 3h–4h.
What are the requirements for the parts of the microwave digestion vessel to be placed in the laboratory?
Digestion vessels, outer sleeves, outer frames and other components are prohibited from being placed in a fume hood for a long time to prevent acid mist from adhering and corroding the components; all parts of the digestion vessel can be placed in a cool and dry place.
