Characterization of a potato reference material for major, minor and trace elements

A potato reference material (RM) was prepared for the analytical quality control program to be employed by the Sub-network on Trace Elements in Food of the FAO European Co-operative Network on Trace Elements. Approximately 50 kg of commercially avialable potato granules prepared from baked, mashed and roller-dried potatoes, containing 2.8 per cent ash and 3 mg/kg added butylhydroxy-anisole was purchased. The granules were carefully homogenised in large glass cylinders followed by division into 50 g portions into numbered acid-washed bottles. The bottled material was tested for homogeneity by taking ten bottles throughout the bottling line and determining by validated atomic absorption spectrometric methods 1.0 g sampled for seven mineral elements. Homogeneity for Mg, Ca, Zn, Fe, Mo, Ni and Cs was better than 5 per cent. An international network of experienced, high-quality reference laboratories was established to conduct an interlaboratory comparison study on the determination of 14 mineral elements in RM. A total of seven methods based on independent analytical principles were employed by the reference laboratories. After excluding outlying analytical results, the criteria defined by the IAEA were used for classification of the overall medians obtained through the interlaboratory comparison study. The relative deviations for the 95 per cent confidence limits of the medians were as follows: P = 4.2 per cent, K = 0.7 per cent, Na = 4.7 per cent, Ca = 5.5 per cent, Mg = 2.4 per cent, Fe = 9.3 per cent, Mn = 4.0 per cent, Zn = 3.6 per cent, Cu = 4.7 per cent, Mo = 23 per cent, Ni = 22 per cent, Cr = 19 per cent, Pb = 11 per cent and Cd = 4.6 per cent. With the exception of Cr, all of the recommended concentration values obtained for the above indicated elements fell into category A, i.e. values recommended with a high degree of confidence according to the classification criteria of the IAEA. The present RM is the only certified potato RM currently available for mineral elements