Extraction kits are used to extract a soil or homogenate. After sample grinding, the sample is extracted in an organic solvent. Buffers can be added to the tube to help define the pH and stabilize labile analytes. Magnesium or sodium sulfate forces phase separation of the organic and aqueous phase. After extraction, the tubes are centrifuged to separate the homogenate from the extraction solution. Dispersive solid phase extraction then removes the matrix before analysis.