Development and metrological evaluation of a certified reference material (CPP-23) for multi-element analysis of cereal plant tissue powder

Accurate determination of macro- and micronutrients in cereal plant tissues is essential for crop nutrition management, environmental monitoring, and interlaboratory data comparability. Despite the availability of plant-based certified reference materials worldwide, no CRM currently exists for Moroccan cereals from semi-arid and arid regions covering both major and trace elements. To fill this gap, we developed and certified a new Certified Reference Material, Cereal Plant Powder 2023 (CPP-23), specifically designed for multi-element analysis of wheat and barley tissues. Composite cereal samples collected from diverse Moroccan agro-ecological regions were air-dried, milled (< 0.5 mm), homogenized, and bottled under controlled conditions. Homogeneity and stability were assessed according to ISO 33405:2024, showing no significant variations under short-term and long-term conditions. Elemental characterization was performed using microwave-assisted digestion followed by ICP-AES for macro- (N, P, K, Ca, Mg, Na) and microelements (Cu, Mn, Fe, Zn, B), with Kjeldahl analysis for total nitrogen. Analytical validation confirmed linearity (R² > 0.999), repeatability (RSD < 2%), and accuracy verified against certified reference materials. An interlaboratory comparison involving eight ISO/IEC 17025-accredited laboratories was conducted following ISO 13528 (Algorithm A) to assign certified values and estimate uncertainties, with expanded uncertainties (k = 2, 95% CL) below 15% for all analytes. CPP-23 meets ISO 17034 requirements, providing a traceable, statistically validated standard for the calibration, quality control, and method validation of multi-element analysis in agricultural and environmental laboratories.