Stas-Otto Procedure
Definition
Classical 1851/1856 acid-base liquid-liquid fractionation. Acidify with tartaric acid and extract acidic and neutral organics into ether, then alkalise and extract bases into chloroform. Yields four fractions used to separate barbiturates, phenols, alkaloids and volatiles.
- Origin years
- 1851, modified 1856
- Acidify with
- Tartaric acid
- Fraction count
- Four
- Separates
- Barbiturates, phenols, alkaloids, volatiles
Common questions
How does the Stas-Otto procedure separate barbiturates from alkaloids in the same sample?+
The tartaric acid step extracts acidic and neutral compounds like barbiturates and phenols into ether, and only after the residue is made alkaline do basic compounds like alkaloids partition into chloroform, so the four fractions correspond to distinct chemical classes rather than a single blended extract.
What is the practical limitation of the Stas-Otto procedure compared to modern extraction?+
It is labour-intensive, uses large solvent volumes, and its yield depends heavily on operator technique, which is why laboratories now generally prefer solid-phase extraction for routine casework and keep classical liquid-liquid partitioning as a fallback or teaching method.
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