What is Wet Digestion? What are the main technologies for wet digestion?

Hello landlord: There are mainly the following types of wet digestion methods: nitric acid digestion method, nitrate perchloric acid digestion method, nitrate monosulfuric acid digestion method, sulfuric acid monophosphoric acid digestion method, sulfate potassium permanganate digestion method, multiple digestion method, alkali decomposition method.

There are mainly the following types of wet digestion methods. (1) Nitric acid digestion method For cleaner water samples, nitric acid can be used for digestion. An appropriate amount of concentrated nitric acid was added to the mixed water sample, heated and boiled on an electric hot plate to obtain a clear and transparent, light-colored or colorless test solution.

Steamed until nearly dry, remove and add 20ml of 2 nitric acid (or hydrochloric acid) after a little cooling, and cool the filtered filtrate to room temperature for later use. (For more technical information related to quality testing, analysis and testing, chemical stoichiometry, and reference materials, please refer to the reference substance query of the China Institute for Inspection and Inspection.)

2) Nitric acid-perchloric acid digestion method Both acids are strong oxidizing acids, and the combined use of water samples containing refractory organic matter can be digested. Take an appropriate amount of water sample and add nitric acid, heat it on an electric hot plate, and digest it until most of the organic matter is decomposed. Remove and add perchloric acid after a little cooling, and continue to heat until white smoke begins.

When the white smoke is exhausted (not steamed to dry up), the sample is taken off and cooled, 2 nitric acid is added, and the filtrate is cooled to room temperature for later use. (3) Nitric acid monosulfuric acid digestion method Both acids have strong oxidation ability, among which nitric acid has a low boiling point and sulfuric acid has a high boiling point. The commonly used ratio of nitric acid to sulfuric acid is 5:

2。This method is not suitable for the treatment of water samples that are susceptible to the formation of poorly soluble sulfate components (e.g., lead, barium, strontium). (4) Sulfuric acid monophosphoric acid digestion method The boiling point of the two acids is relatively high, among them, the oxidation of sulfuric acid is strong, and phosphoric acid can be complexed with some metal ions such as iron ions, so the combination of the two to digest water samples is conducive to eliminating the interference of iron plasma during the determination.

5) Potassium permanganate sulfate digestion method This method is often used to digest water samples for the determination of mercury. Potassium permanganate is a strong oxidant, which can oxidize organic matter under neutral, alkaline and acidic conditions, and its oxidation products are mostly oxalate, but it can continue to oxidize in acidic media. (6) Multiple digestion methods In order to improve the digestion effect, in some cases, it is necessary to use more than three acids or oxidants to digest the system.

For example, when processing a water sample for total chromium, it is digested with sulfuric acid, phosphoric acid, and potassium permanganate. (7) Alkali decomposition method When the loss of volatile components is caused by the digestion of water samples with acid system, the alkali decomposition method can be used instead, that is, sodium hydroxide and hydrogen peroxide solution, or ammonia and hydrogen peroxide solution are added to the water sample, heated and boiled until nearly dry, and dissolved with water or dilute alkali solution.

Using a liquid or a mixture of liquid and solid as an oxidant to decompose the organic matter in a sample at a certain temperature is a process called wet digestion.

A method of decomposing and oxidizing organic matter in soil or plant samples with inorganic strong acids and/or strong oxidant solutions to convert the components to be measured into measurable forms.

Wet digestion (wetdigestion; wetmineralization] is a method of decomposing and oxidizing organic matter in soil or plant samples with inorganic strong acids and/or strong oxidant solutions to convert the components to be measured into measurable forms, which is a method that replaces dry digestion to prepare samples for full analysis of elements. Commonly used oxidizing acids and oxidants are concentrated nitric acid, concentrated sulfuric acid, perchloric acid, potassium permanganate, hydrogen peroxide, etc. The heating equipment used for wet digestion includes electric furnaces, water baths, oil baths, electric hot plates and microwave digestion instruments.

Wet digestion: dissolve the sample with acid, generally through an electric hot plate through quasi-temperature control heating, non-closed digestion.

Microwave digestion: dissolve the sample with acid, use microwave digestion instrument to digest, the temperature control is good, and at the same time, it is a closed digestion.

Dry digestion: no acid is used for digestion, mainly used for some specific samples, such as wheat and other organic matter.

Answer]: Wet digestion is the use of various acids or bases for digestion, commonly used wet digestion includes:

1) Nitric acid digestion method, the applicable water sample is a cleaner water sample;

2) Nitric acid-perchloric acid digestion method, the applicable water sample is a water sample containing refractory organic matter;

3) Nitric acid-sulfuric acid digestion method, which is not suitable for water samples that are easy to generate incomprehensible and rapidly soluble sulfate components (such as lead, barium, strontium);

4) Sulfuric acid-phosphoric acid digestion method, the applicable water sample is the water sample containing Fe3+ equivalence verition;

5) sulfuric acid-potassium permanganate digestion method, the applicable water sample is the water sample for the digestion and determination of mercury;

6) Multivariate digestion method, which refers to the digestion system composed of more than ternary acids or oxidants, such as sulfuric acid, phosphoric acid and potassium permanganate when treating and measuring water samples of total chromium;

7) Alkali decomposition method, when the acid system is easy to cause the loss of volatile components due to the digestion of water samples, the alkali decomposition method can be used instead.

At present, there are many wet digestion methods, and different digestion equipment can be selected according to different samples, and different digestion methods can be formulated to achieve an accurate, efficient and rapid test result. All digestion should be carried out in the following aspects: 1. To avoid the loss of the components to be measured; 2. Do not introduce interfering substances; 3. Be safe and fast, and do not bring difficulties to the follow-up operation steps; 4. The solution obtained after digestion must be easy to detect.

In this way, the above different digestion equipment and methods can be selected according to the experimental requirements! <

Wet digestion is currently the most direct, effective and economical method of sample preparation for elemental analysis, with the innovation and development of laboratory equipment technology. Bore digester and microwave technology will be the two mainstream experimental equipment products for laboratory wet digestion!

There are many methods of wet digestion, and different methods will be selected for different samples and different instruments and equipment. At present, the samples of wet digestion can be divided into three categories: samples with high organic content, samples with low organic content, and samples that are simple and easy to digest.

The choice of acid system is different for different samples! Hydrochloric acid is suitable for the digestion system below 80, nitric acid is suitable for the digestion system of 80-120, sulfuric acid is suitable for the digestion system of about 340, hydrochloric acid-nitric acid mixed acid is suitable for the digestion system of 95-110, nitric acid-perchloric acid is suitable for the digestion system of 140-200, nitric acid-sulfuric acid is suitable for the digestion system of 120-200, and nitric acid-hydrogen peroxide is suitable for the digestion system of 95-130. Choosing the right acid system is very important to speed up the destruction of organic matter, and at the same time, accurate temperature control is required to achieve the desired digestion effect!

Wet digestion is a method of destroying organic or reducing substances in a sample with an acid or lye solution and under heating conditions.