New measurement standard will raise quality of GMO testing
The JRC Institute for Reference Materials and Measurements works continuously to improve both reliability and comparability of laboratory testing results. It has now introduced a new set of reference materials for testing maize line MON 810 genetically modified organisms (GMOs) in food and feed samples by control laboratories. The new materials comprise the first-ever available set of certified quality assurance tools for GMO measurements expressed in a new measurement unit - as laid out in the EC recommendation 2004/787/EC in 2004.
The recommendation proposes to express quantification results for food and feed products containing genetically modified (GM) products in copy numbers. Modern analytical techniques such as real-time polymerase chain reaction (PCR) measure copy numbers of DNA sequences in the GM event relative to a DNA sequence of the species. Sensitivity and the ability to detect GM products also in processed food and feed have made real-time PCR the method of choice for quantification of GM content. This has resulted in a recommendation of the European Commission to change the expression of the quantification results from mass fractions (mass of GM material per total mass of the species) to copy number ratios (number of GM DNA sequences per number of DNA sequences of the species).
The implementation of the recommendation, however, depends on the availability of suitable quality assurance tools. For correct application of the detection methods (e.g. the international standard methods) and to comply with laboratory accreditation schemes (e.g. ISO/IEC 17025) laboratories need reference materials certified for their GM content expressed in the same measurement unit i.e. the copy number ratio. Therefore, IRMM has now developed and certified an existing reference material ERM®-BF413d for its MON 810 copy number ratio and is preparing the certification of GM matrix materials and calibrants for other GM events.
The ERM®-BF413d matrix material is a mixture of ground MON 810 GM seeds and ground non-GM maize seeds, and is intended for the quality control of the MON 810 quantification method of the International Organization for Standardization (ISO 21570:2005, Annex D2). To provide an independent calibrant the reference material ERM®-AD413 made up of plasmid DNA has been certified to contain one copy of each of the two DNA sequences targeted by the ISO MON 810 quantification method. Prior investigations have demonstrated that for this specific method plasmid DNA is a suitable calibrant i.e. it is commutable.
Together, the two certified reference materials can ensure correct implementation of the entire MON 810 measurement procedure and form the first set of GM reference materials available world-wide certified for their copy number ratio. Due to the novelty, the two reference materials are released together with an ERM® application note describing the correct use of the calibrant and the matrix material.