Search

An inter-comparison exercise was performed between two laboratories on mineralized moss samples. Ten samples, together with three certified reference materials (CRM 61, CRM 62 and CRM 482) and five blanks were mineralized independently in the two laboratories and then analysed by both with different techniques (AAS, ICP-MS, and INAA). The elements analyzed were: Cd, Cr, Cu, Fe, Ni, and Pb. Accuracy tests showed that, for AAS, the relative standard deviations for five repetitions of the same sample were between 0.2 I for Cd and 2.9 % for Cr and that the concentration values found for reference materials were within one standard deviation from the certified values, with the exception of Cr and Cd for CRM 482. The statistical analysis was performed first with a simple linear regression and a Student t-test taking into account the possible influence of the mineralization procedure and ofthe analytical technique, in order to evaluate their reliability. The results showed that more than 78 % of the regressions had a correlation coefficient higher than 0.750, and that 83 % of the slopes were not different from ogre with a level of significance of 0.01. Afterwards, the precision of the measurements were evaluated using maximum likelihood; the normalized errors showed that 1CP-MS had a better performance on most of the elements analysed (with the exception of Fe) aril that both the mineralization procedures gave satisfactory results. The two laboratories were then found to produce reliable results. [ABSTRACT FROM AUTHOR]