Stas-Otto Method
Definition
Sequential acid-alkaline solvent partitioning that isolates organic poisons from biological matrix in two fractions: acidic ether (Fraction A) for acidic and neutral drugs, and alkaline chloroform (Fraction B) for alkaloids. Developed by Jean Servais Stas in 1851 and modified by Julius Otto.
- Developed by
- Jean Servais Stas, 1851
- Modified by
- Julius Otto
- Fraction A
- Acidic ether, for acidic and neutral drugs
- Fraction B
- Alkaline chloroform, for alkaloids
Common questions
Why does the Stas-Otto method use two separate solvent fractions?+
Acidic and neutral compounds partition preferentially into ether under acidic conditions, while alkaloids and other basic compounds only partition into an organic solvent once the sample is made alkaline, so splitting extraction into two pH-dependent steps recovers both compound classes.
Is the Stas-Otto method still used in modern toxicology?+
Its acid-base partitioning principle remains foundational to sample clean-up before instrumental analysis, though modern labs generally follow more standardised or automated liquid-liquid and solid-phase extraction variants rather than the original 19th century procedure.
Related terms
- Ammonium Sulphate Modification
- The Otto variant in which saturated (NH4)2SO4 is added to a protein-rich homogenate (liver, kidney, blood) to salt out proteins before partitioning....
- Colour Spot Test
- A presumptive identification reaction in which a small amount of concentrated fraction is treated with a chromogenic reagent (Marquis, Mecke, Mandelin, Mayer,...
- Defatting
- A clean-up step before partitioning in which the acidified aqueous is washed with petroleum ether or n-hexane to remove fats, waxes and...
- Fraction a
- The acidic ether extract obtained by partitioning the acidified aqueous tissue digest with diethyl ether at pH 2 to 3. Contains barbiturates,...
- Fraction B
- The alkaline chloroform extract obtained after basifying the residual aqueous to pH 9 to 10 with ammonium hydroxide and partitioning with chloroform....