Assessment of sampling and analytical quality control in determination of Al in soils using chemical extraction

The bias and the precision of the analytical method used were initially ass essed using reagent blanks and duplicate analyses of each sample. Furthermo re, a sampling and analytical quality control scheme (SAX) was conducted an d robust analysis of variance (ANOVA) was used to estimate the proportions of random errors introduced by sampling and analytical procedures. The resu lts show that the precision of measurement and analysis, though worse than the traditional target of 10%, was good enough for a clear description of g eochemical variation between sample sites. The effect of Al contamination s eemed to be more sensitive in the chemical analysis than in sampling proced ure, Moreover, the application of SAX to the study suggests that the analyt ical precision required must be judged by comparison with both sampling pre cision and true geochemical variation. (C) 1999 Academic Press.