Recently I read a paper (link is present below), where they mentioned that " Grain labs often remove impurities from samples before conducting a test. However, the purification of GMO samples is not allowed" but they did not give any reference. Can someone help me that which guidelines they might have used?
https://www.romerlabs.com/en/knowledge-center/knowledge-library/articles/news/the-7-sins-of-gmo-testing/