Ammonium Sulphate Modification
Definition
The Otto variant in which saturated (NH4)2SO4 is added to a protein-rich homogenate (liver, kidney, blood) to salt out proteins before partitioning. Breaks emulsions and releases drug bound to plasma protein, improving recovery in viscera workups.
- Parent method
- Stas-Otto extraction
- Reagent
- Saturated (NH4)2SO4
- Mechanism
- Salts out proteins
- Typical matrix
- Liver, kidney or blood homogenate
- Applied before
- Solvent partitioning step
Common questions
Why does salting out improve drug recovery in viscera cases?+
Many drugs, especially basic ones, bind to plasma and tissue proteins. Precipitating those proteins with saturated ammonium sulphate frees bound drug into solution and breaks up protein emulsions that would otherwise trap analyte at the solvent interface during extraction.
Is this step used with modern instrumental workups too?+
It remains useful for putrefied or protein-rich viscera where emulsion formation is severe, but many contemporary labs favour solid-phase extraction or QuEChERS-style cleanup for routine casework and reserve the classical salting-out step for difficult samples.
Related terms
- 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....
- Stas-Otto Method
- Sequential acid-alkaline solvent partitioning that isolates organic poisons from biological matrix in two fractions: acidic ether (Fraction A) for acidic and neutral...