Ash (analytical chemistry)

In analytical chemistry, ashing is the process of mineralization for preconcentration of trace substances prior to chemical analysis.^[1] The residues after a sample is completely burnt - in contrast to the ashes remaining after incomplete combustion - consist mostly of metal oxides.

Ash is one of the components in the proximate analysis of biological materials, consisting mainly of salty, inorganic constituents. It includes metal salts which are important for processes requiring ions such as Na⁺ (Sodium), K⁺ (Potassium), and Ca²⁺ (Calcium). It also includes trace minerals which are required for unique molecules, such as chlorophyll and hemoglobin.

Example

For instance, the analysis of honey shows:^[2]

Typical honey analysis

• Fructose: 38%
• Glucose: 31%
• Sucrose: 1%
• Water: 17%
• Other sugars: 9% (maltose, melezitose)
• Ash: 0.17%

In this example the ash would include all the minerals in honey.

References

1. IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "ashing".
2. Sugar Alliance

See also

• Oxides, e.g. Al₂O₃, CaO, Fe₂O₃, MgO, MnO, P₂O₅, K₂O, SiO₂
• Carbonates: Na₂CO₃ (soda ash), K₂CO₃ (potash)
• Bicarbonates, e.g. NaHCO₃ (baking soda)
• Sulfates: sulfate ash according to Ph. Eur.