SAMPLING AND ANALYTICAL QUALITY-CONTROL OF THE DETERMINATION OF ALUMINUM IN SOYBEAN LEAVES

A pot trial was set up with nine soil types, each replicated five time s, in randomized blocks, to investigate the effect of soil properties on the uptake of Al by soybean plants, The variance of the measurement s was estimated using five replicates of each soil type, This then ena bled the statistical significance of the difference between results fo r each soil type to be established, The analytical variance was determ ined by two analyses per pot, Systematic errors during the analytical procedure were estimated by the analysis of reagent blanks and CRMs. A nalysis of variance (ANOVA) was used to estimate the proportions of to tal variance contributed by analysis, sampling and geochemistry, Robus t statistics were required because of the high sensitivity of classica l ANOVA to a small number of outlying values, due to either technical or geochemical causes, In the case study described here, traditional a nalytical quality control apparently gave a satisfactory result, Howev er, the results from robust ANOVA showed. that the sampling error was the limiting factor for this application, It is suggested that the env ironmental analyst must consider errors from procedures of both sampli ng and analysis of environmental samples.