CERTIFICATION OF CABBAGE AND CARNATION SAMPLES AND THEIR USE IN AN INTERNATIONAL PROFICIENCY STUDY

The preparation of carnation straw (Dianthus) and white cabbage (Brassica oleracea) as reference plant materials for chemical analysis and the testing of their homogeneity is described. The elemental content has been determined and evaluated by the Comite Inter-Instituts (CII) using different analytical procedures. The CII is an organisation grouping about 30 selected European laboratories which prepares, on a regular basis, several, very different reference plant materials. At the moment about 24 different plant samples are in stock. Recommended values for the two samples used in this study, are given for ash content, N, P, K, Ca, Mg, Na, Al, Fe and Mn. For 3 years these materials have been used as home references in the International Plant-analysis Exchange (IPE), a continuous proficiency testing scheme, organized by the Wageningen Agricultural University (The Netherlands), in which 230 laboratories worldwide are participating. The values found by the IPE laboratories are compared with the values recommended by CII and are mostly in good agreement with each other.