Twenty five years of reference material activity at Agriculture and Agri-Food Canada.

In the mid 1970s, the available RMs, notably Bowen's Kale and Orchard Leaves and Bovine liver from National Bureau of Standards (NBS), although of great benefit, were overwhelmingly insufficiently representative, in respect of matrix and elemental composition, of the wide range of natural products submitted for analysis and in worldwide commerce. To provide additional coverage, an RM development project was initiated with input from cooperating analysts leading to an Agriculture and Agri-Food Canada/National Institute of Standards and Technology (NIST) cooperative venture and development of a total of 12 different agricultural/food RMs. With a total of 303 concentration values for 34 elements and a wide range of matrix components such as ash, silica, protein, fat, carbohydrate and fiber, these RMs significantly augment the world repertoire of biological control materials. A final material under consideration is a highly reliable, discrete, synthetic RM for quality control and calibration. This paper summarizes the research and developmental activities undertaken during the past quarter of a century related to RM development at Agriculture and Agri-Food Canada and includes a short historical background, conceptual considerations, preparation, physical characterization, homogeneity estimation, chemical characterization, calculation of recommended reference values and associated uncertainties, methodology development and application, and performance of inorganic analytical methods in a multielement, multilaboratory, collaborative characterization campaign.