ISO 20837:2006 provides criteria and examples for sample preparation in order to obtain PCR-compatible samples or nucleic acids of suitable quality and quantity for PCR. It provides a description of the general principles involved. References to standards concerning the enrichment of microorganisms are given in Annex A, and a detailed method for DNA extraction is given in Annex B. ISO 20837:2006 has been established for food matrices, but could also be applied to feed and agricultural/environmental matrices with some adaptations, if necessary.