Acid digestion is the most common wet-chemical sample preparation technique. By using concentrated acids or mixtures thereof, the matrices of organic and inorganic samples can be totally destroyed or dissolved, and the whole sample can be brought into solution. Subsequently, the concentration of elements or species can be determined with an adequate analytical technique, e.g. AAS (atomic absorption spectroscopy), MIP-OES (microwave-induced plasma optical emission spectrometry), ICP-OES (inductively coupled plasma optical emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry)[2].
Find the most commonly used acids for acid digestion and their typical concentrations below[3]:
- Nitric acid, HNO3 (65 %)
- Hydrochloric acid, HCl (30 % to 37 %)
- Hydrofluoric acid, HF (40 % to 48 %)
- Sulfuric acid, H2SO4 (95 % to 98 %)
- Perchloric acid, HClO4 (70 % to 72 %)
- Phosphoric acid, H3PO4 (85 %)
- Hydrogen peroxide, H2O2 (30 %)
- Aqua regia, HCl + HNO3 (volume ratio 3:1)
- Reverse aqua regia, HCl + HNO3 (volume ratio 1:3)
- Boric acid, H3BO3 (approx. 5 %)