Analytical accuracy, precision and detection limits determined from samples (CRMs; blanks) subjected to a nitric-perchloric acid digestion.

alaterite soil produced by the National Research Centre for Certified Materials, China;bGreen River shale produced by U.S. Geological Survey;ccalculated as 3 x standard deviation of mg/l blank values multiplied by appropriate dilution factor;ddefined here as the deviation of the measured observation from the true (certified) value, and calculated as (mean of five measurements/certified) x 100%;eprecision = coefficient of variation (%) determined from five replicates of one sample;fcannot be calculated since below detection limits.