Determination of Percentage of RoundUp Ready registered Soya in Soya Flour Using Real-Time Polymerase Chain Reaction: Interlaboratory Study

An interlaboratory study was conducted to evaluate a method for determination of the percentage of RoundUp Ready registered (RR) soya in soya flour using Taqman registered technology. The method included DNA extraction from the test portion with cetyltrimethylammonium bromide buffer followed by chloroform extraction and Wizard registered resin cleanup steps. The DNA was then assayed with primer and probe sets specific for lectin as the endogenous control and the RR insert as the target. The percentage of RR soya in the soya fraction of the sample was calculated by using a matrix- matched standard curve. Ten samples of split-level blind duplicates were sent to 22 laboratories in 12 countries worldwide. Test portions contained 0, 0.5, 0.7, 1.6, 2, and 3.9% (w/w) RR soya prepared gravimetrically from commercially available RR standard reference materials. Based on the results for test materials, the relative standard deviation for repeatability (RSD sub(r)) for the method ranged from 9.3 to 19.3% and, for reproducibility (RSD sub(R)), ranged from 20.3 to 33.7%.