Using atomic absorption spectrometry techniques and microwave digesters, traditional methods for acid digestion are followed, and they are used for developing and preparing samples, in order to obtain the analysis in liquid form.
This action is carried out with acids, to achieve complete oxidation and reduce interference caused by organic matter. Because of these, the determination of the metals is developed, heating in stages, first, the water is removed, the product is carbonized and finally it is incinerated in muffle furnace.
Similarly, acid digestion offers development mechanisms, accompanied by chemical components, digestion systems and favorable characteristics, for the determination of metals.
Functions of Acid Digestion
The basic principle of acid digestion is related to the oxidative loss of the sample matrix, in which they are usually boiled with an acid at a high temperature and remove the substance to be determined, and after analysis.
The microwave digester is therefore used to dissolve the samples. By placing them in a concentrated acid inside a tight container and exposing them to microwave radiation, the material can be determined.
Both the speed of thermal decomposition of the sample and the dissolution of metals increase once they are in solution, and they can be quantified by spectroscopic techniques. In the acid digestion process, the sample preparation time is reduced by 50 – 75% compared to traditional methods.
It should be noted that acid digestion by microwave offers advantages to accurately record parameters such as pressure or temperature, or the possibility of digesting in very short times, since the rate of heating and cooling is very high.
Acid Digestion of Metals
Assisted acid digestion for metal determination, is one of the procedures applied for metal extraction in solid prototypes, involves the use of mineral acids, oxidants and an external microwave source of heating to break down the sample. The choice of acids and the use of microwaves depends on the nature of the matrix.
- Nitric acid: Nitric acid is the most recommended for sample digestion, where boiling temperature is relatively low, but with the use of closed containers, is another alternative to increase temperature and improve digestion efficiency.
- Hydrochloric acid is a non-oxidant acid with weak reducing properties and is frequently used for the breakdown of inorganic matrices. Dissolves carbonates, phosphates, borates, sulfates (except barium sulfate) and metal oxides.
- Hydrofluoric acid: is considered an important chemical reagent for improving the breakdown of mineral compounds, and is mixed with other acids, mainly nitric acid.
- Perchloric acid: is one of the strongest mineral acids and presents a high oxidizing power at high temperatures. It must be handled with extreme care because of its rapid reactivity and can sometimes become explosive. Perchloric acid can be broken down at 245 °C in a closed microwave container and dangerous amounts of gas by-products and excess pressure can develop.
- Sulfuric acid: is a strong dehydrating reagent, and has the highest boiling temperature of mineral acids used for digestion. For this reason, a long time of evaporation is required to remove excess acid.
Kalstein Brand Microwave Digester
We at Kalstein, are trained to meet the demands of our users, in terms of the selection of laboratory equipment. We offer you, the Microwave Digester System, corresponding to the YR series, which has attractive features, such as: The continuous 360º rotor performs the rotation in the same direction. Ensures uniform and complete digestion, also reduces engine wear, greatly prolonging engine life. The 7-inch color LCD touch screen displays real-time temperature and pressure, as well as working time and trend curves. The material in the sample digestion container is imported PFR. For the outer protective container, PEEK and fiberglass are imported which could prevent corrosion by high temperature, high pressure and acid.
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