Glossary
What is Residue on Ignition (Sulfated Ash)?
A test measuring the non-volatile inorganic residue left after a sample is ignited with sulfuric acid, which converts metals to their sulfates. It gives a general indication of inorganic contamination in organic substances. Pharmacopoeias typically limit it to 0.1% or less for APIs. The European Pharmacopoeia calls the test sulfated ash.