Why nitric acid is used for digestion?
Nitric acid is used because all nitrate salts are soluble in water. If we use H2SO4 or HCl they will produce sulphate or chloride salts. Some metal sulphates and chlorides are not very soluble in water.
What is the acid digestion method?
Open vessel acid digestions have long been a popular and simple method for the digestion of inorganic and organic sample materials in chemical laboratories. It refers to acid attack in open containers or screw-top vials (low pressure) placed on a hot plate.
What is microwave assisted acid digestion?
Acid digestion is one of the most important sample preparation techniques. Analytical equipment which is able to determine small concentrations of toxic metals requires a clear, particle-free, slightly acidic solution.
How do you digest a water sample for heavy metal analysis?
Cover samples with a reflux cover or watch glass and digest for 2.0 – 2.5 hours at 95 ± 5°C (this excludes the time needed to pre-heat the samples to 95°C). The heat for digestion must maintain the sample extract temperature at 95 ± 5°C.
Does nitric acid dissolve everything?
Nitric acid is the primary choice here on several grounds. It is an oxidizing acid that can dissolve most metals to form soluble metal nitrates. It has poor oxidizing strength below 2 M but is a powerful oxidizing acid in concentrated form.
What happens when you mix nitric acid and hydrogen peroxide?
2NO + 3 H2O2 → 2HNO3 + 2H2O 2NO2 + H2O2 → 2HNO3 Concentrated nitric acid is also used to passivate equipment for use with hydrogen peroxide. While nitric acid and hydrogen peroxide are both hazardous chemicals, there are additional hazards that can arise when they are mixed together.
What is wet ashing?
Wet ashing is a procedure for oxidizing organic substances by using acids and oxidizing agents or their combinations. Minerals are solubilized without volatilization. Wet ashing is often preferable to dry ashing as a preparation for specific elemental analysis.
What is aqua regia digestion method?
Aqua Regia is a partial digestion using nitric and hydrochloric acid at a 1:3 ratio. The digestion is carried out at relatively low temperatures which allows Hg, which is volatile at higher temperatures, to be analysed at the same time as the multi- element suite.
How does microwave digestive system work?
Microwave digestion works by exciting nearby water molecules to tear sample materials apart. Adding strong acids, or even a base, speeds up sample homogenization.
How do you clean a microwave digestive vessel?
Microwave tubes or vessels are cleaned after each use by soaking in the 10% Nitric Acid bath in GWC 675 for at least 2 hours after each use. They should then be rinsed 3 times in Reverse Osmosis (RO) water. After this rinse set tubes in bins to dry.
Why is acid digestion used in heavy metal analysis?
Acid digestion procedures are required for the quantification of heavy metals in the solid samples such as soils, sediments and sludges. Numerous studies have been developed to improve the most accurate methods for proper extraction of chosen elements.
What is the difference between wet digestion and dry ashing?
Dry ashing was carried out by heating the sample at 500 °C and dissolving the sample in HNO3 while wet digestion was done by heating the sample at 100 °C with HNO3, HClO4 and H2SO4 as oxidizer solutions.