Preserving IP product Purity
See this article from the Organic and Non-GMO report about testing in this new post-labeling law world. With all the new focus on identity-preserved grains and organic food, there is an increased need for testing at all facilities in the IP grain chain; in addition to the farmers themselves, this includes transporters and elevator operators. At each step of the process it is important to have procedures in place to ensure the purity of the product. See this article about combine cleaning. In addition to physical changes and cleanliness, testing is also paramount. The two main types of testing available are test strips and PCR testing.
Test Strips vs PCR Testing
Protein-based lateral flow strip tests are used to detect the presence of a particular GMO. The test is fast (a few minutes), but does not provide results concerning the level of impurity. On the other hand, DNA-based polymerase chain reaction (PCR) tests do provide quantitative analysis, but cost much more and can take up to three days to complete.
The non-gmo project maintains a list of recommended testing facilities for GMOs. There are also some new products on the horizon in the PCR realm, including DNAble from Envirologix (not a lab, per se, but a testing kit manufacturer) which gives results similar to PCR (high sensitivity with high specificity) on-site in much less time (presently, for soybeans).