What is the function of digestion?

Digestion, also known as wet digestion, is a method of destroying organic or reducing substances in samples with acid or lye under heating conditions. Commonly used acidolysis systems are: nitric acid-sulfuric acid, nitric acid-perchloric acid, hydrofluoric acid, hydrogen peroxide and so on. It can destroy all organic and reducing substances such as cyanide, nitrite, sulfide, sulfite, thiosulfate and thermally unstable substances such as thiocyanate in sewage and sediments; Alkaline hydrolysis uses caustic soda solution. The digestion can be carried out in a crucible (made of nickel and polytetrafluoroethylene) or a high-pressure digestion tank.

The commonly used digestion methods are wet digestion and dry ashing. Commonly used digestion oxidants include monobasic acid system, polybasic acid system and alkali decomposition system. The most commonly used unit acid is nitric acid. The purpose of using polybasic acid is to increase digestion temperature, accelerate oxidation speed and improve digestion effect. In the process of water sample digestion, the acid system should be selected according to the type of water sample and the determination method adopted.

The data extension is due to various kinds of pollution and complex components in environmental samples. Most of the components to be detected have low concentrations and different forms, and there are a large number of interfering substances in the samples. More importantly, with the development of environmental science and technology, the quantitative description of most organic pollutants is completed by comprehensive indicators (such as COD, BOD and TOC). ) can no longer meet the requirements of environmental monitoring. Many organic compounds are persistent, bioaccumulative and toxic pollutants with "three causes" effect. However, the concentration of these organic substances in environmental media is extremely small, which makes little contribution to the above comprehensive indicators, or can not be reflected at all.

This shows that before the analysis and determination, different sample pretreatment is needed to obtain the morphology and concentration of the components to be measured suitable for the analysis method and to separate them from the interfering substances to the maximum extent. When determining inorganic elements in environmental samples (water samples, soil samples, solid waste, particles intercepted in atmospheric sampling, etc.). ), it is necessary to digest environmental samples, destroy organic matter, dissolve particulate matter, and oxidize the elements to be tested in various valence states into univalent states or transform them into easily decomposed inorganic compounds.

References:

Baidu encyclopedia-digestion