Validation of an immunoassay for detection and quantitation of a genetically modified soybean in food and food fractions using reference materials: Interlaboratory study

An immunoassay for detection of a specific genetically modified soybean (Ro undup-Ready(R)) was validated on dried soybean powder in an interlaboratory study. Different percentages of genetically modified soybeans in nonmodifi ed soybean matrix were evaluated in a blind study. Thirty-eight laboratorie s from 13 countries participated, The immunoassay was evaluated for 2 end-p oints: (1) To give a semiquantitative result, i.e., determination of a give n sample above or below a given threshold, or (2) to compute a quantitative result, i.e., percentage of genetically modified soybeans in the sample. S emiquantitative results showed that a given sample which contained <2% gene tically modified soybeans was identified as below 2% with a 99% confidence level. Quantitative use of the assay resulted in a repeatability (r) and re producibility (R) that were computed to be RSDr = 7% and RSDR = 10%, respec tively, for a sample containing 2% genetically modified soybeans. Applicati on of this method depends on availability of appropriate reference material s for a specific food matrix. Only matrix-matched reference materials can b e used for analysis of food or food fractions.