Defatting
Definition
A clean-up step before partitioning in which the acidified aqueous is washed with petroleum ether or n-hexane to remove fats, waxes and neutral lipids. The organic layer is discarded because the analytes are still in the aqueous phase at acid pH.
- Stage
- Clean-up step before liquid-liquid partitioning
- Solvents used
- Petroleum ether or n-hexane
- Removes
- Fats, waxes, and neutral lipids
- Sample condition
- Applied to the acidified aqueous phase
- Method context
- Classical Stas-Otto style extraction schemes
Common questions
Why is the organic layer discarded during defatting rather than kept for analysis?+
At acid pH the target analytes remain ionised and dissolved in the aqueous phase, not the organic layer, so the organic layer at this stage contains only unwanted fats and waxes, and discarding it removes interference without losing any of the compounds of interest.
What happens to a toxicology extraction if the defatting step is skipped?+
Residual lipid material can co-extract with the target analytes in later partitioning steps, fouling chromatographic columns, suppressing ionisation in mass spectrometry, and making downstream quantification less reliable.
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,...
- 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...