Uncertainty assessment including sampling for determination of metals in lichen samples using ICP-OES

The uncertainty arising from the lichen sampling, preparation and analysis was calculated according to a new guide by Eurachem/EUROLAB/CITAC/ Nordest/AMC, 2007, using the retrospective lichen data set completed in 2000 in Turkey. ICP-OES was used to determine the elements Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn. The method validation studies included linearity, detection limits, precision and accuracy. Measurement uncertainties were calculated by applying the bottom-up approach. It was observed that the largest contribution to the uncertainty came from the sampling. This approach indicated that, the standard uncertainties of the concentration values could be as large as 31.5%.