Ch 35: Decomposing and Dissolving the Sample Flashcards
A resistant to heat and attack by strong chemical agents
Refractory substance
When the sample treatment did not dissolve the sample completely because portions of the analyte are retained within the residue
Incomplete dissolution of the analytes
Enumerate the sources of error in decomposition and dissolution
- Incomplete dissolution of the analytes
2.Losses of the analyte by volatilization
3.Introduction of Analyte as a Solvent Contamination
4.Introduction of contamination from reaction of the solvent with the vessel walls
The possibility that some portion of the analyte may volatilize and be lost
Losses of the analyte by volatilization
When the mass of solvent required to dissolve a sample exceeds the mass of a sample and when the analyte present is in trace amount or small concentration, which leads to significant error.
Introduction of Analyte as a Solvent Contamination
An error encountered in decomposition that involved high-temperature fusions
Introduction of contamination from reaction of the solvent with the vessel walls
An inorganic acid that is an excellent solvent for inorganic samples but it limited to decomposing organic materials.
HCl
A process of oxidative decomposition of organic samples by liquid oxidizing reagents, such as HNO3, H2SO4, HClO4, etc
Wet ashing
Is a strong oxidant that dissolves all common metals with the exception of aluminum and chromium
HNO3
An effective reagent for decomposition as a solvent to its high boiling temperature, where most organic compounds are dehydrated and oxidized at this temp
H2SO4
A potent oxidizing agent (has a potentially explosive nature) that when comes into contact with organic materials promotes violent explosions
HClO4
More rapid wet ashing can be obtained by the use of mixture of acids
Oxidizing mixtures
A mixture containing 3:1 of conc. HCl and HNO3
Aqua regia
Use in the decomposition of silicate rocks and minerals
Hydrofluoric acid
The usage of microwave for the decomposition of both organic and inorganic materials, the advantage is the speed of the process.
Microwave decompositions
Microwave digestor that is constructed from low-loss materials that are transparent to microwaves that are thermally stable and resistant to chemical attacks
Moderate-pressure digestions
A schematic of a commercial microwave bomb designed to operate at 80 atm that can be tolerated by the Moderate-pressure vessel
High-pressure microwave vessels
a.k.a open-vessel system; does not have an oven but uses focused microwave cavity
Atmospheric-pressure digestions
designed to heat simultaneously of the moderate-pressure vessel
Microwave Ovens
Developed for performing fusions and for dry ashing samples that contains organic materials before acid dissolution
Microwave furnaces
The process of oxidizing an organic sample with oxygen or air at high temperature
Dry ashing
Is the thermochemical decompositions of organic compounds at elevated temperature in the absences of oxygen
Pyrolysis
Is the thermochemical decompositions of organic compounds at elevated temperature in the presence of oxygen
Combustion
sample is mixed with an alkali metal salt
flux
Fused to form a water soluble product
melt
A type of fluxes that coverts the cationic constituents of the sample to acid-soluble carbonates or oxides
Sodium carbonate
A potent acid flux that is particularly useful in attacking the more intractable metal oxides
Potassium pyrosulfate
Use for attacking refractory silicate and alumina minerals
Lithium metaborate
