FORESTRY CANADA INTERLABORATORY STUDY FOR THE ANALYSIS OF PLANT MATERIALS

Eighteen laboratories participated in this round-robin performance tes t, commissioned by the Quality Assurance Sub-roup, to assure comparabi lity of results in the inorganic constituents in plant materials. Each laboratory was provided with an identical set of ten oven-dried, blin d audit samples (sets included foliage, bark, stem wood and leaf litte r), and was asked to analyze the samples for total concentrations of C , N, P, K, Ca, M-, S, Fe, Mn, B, Zn, Cu, Mo, Cl, Na, Al, Ni, Pb, Cd, H -, Co, and As. The data were analyzed for group statistics (means, med ians, standard deviations and standard errors by sample and element) a nd distributed to the participants for selfevaluation. Laboratory conf identiality was maintained throughout. On average, coefficients of var iation suggested reasonable reproducibility among laboratories with re spect to C, P, K, Ca, M-, Cu, and Al; some laboratory-to-laboratory va riation with respect to N, S, Fe, Mn, and Zn; and considerable laborat ory-to-laboratory variation with regard to other elements. In general, samples with low concentrations presented difficulties.