Extraction methods are often used for the determination of fat in food and feed. The physical separation process is also used in environmental and residue analysis and for the quality control of production materials. The substance to be determined is dissolved out of the sample using a suitable solvent and separated from the solvent. The resulting extract can now be determined quantitatively or qualitatively.
For example, petroleum ether, hexane or diethyl ether are used for the extraction of fats and oils from food and feed. The methods used here are called the Röse-Gottlieb principle, fat content according to Schmid-Bondzynski-Ratzlaff (SBR), total fat according to the Weibull-Stoldt or Weibull-Berntrop principle or, in the feed sector, raw fat determination by Weender analysis. Organic pollutants can be extracted from various types of samples with hexane, acetone or toluene or mixtures thereof.
Extraction processes are often time-consuming and the handling of solvents is dangerous. Automatic systems such as the SOXTHERM are many times faster than the conventional Soxhlet method and can considerably reduce the workload of laboratory staff. The operating principle of automatic extraction can be divided into 5 stages.
The sample is immersed in boiling solvent and the extractable material is liberated from the sample.
The level of the solvent is lowered below the extraction thimble. The excess solvent is collected in the rear solvent recovery tank.
The material is extracted by the refluxed, condensed solvent and is concentrated in the extraction beaker.