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Original scientific paper

Beech Leaves (Fagus Sylvatica L.), Reference Sample of ICPForests and itsApplicability in Determination of Total Nitrogen and Carbon in Leaves

Tamara Jakovljević ; Hrvatski šumarski institut
Gábor Pánczél ; Hungarian Forest Reserach Institute, Budimpešta, Mađarska
Miklós Manninger ; Hungarian Forest Reserach Institute, Budimpešta, Mađarska
Nenad Potočić ; Hrvatski šumarski institut
Ivan Seletković ; Hrvatski šumarski institut
Tomislav Dubravac ; Hrvatski šumarski institut
Marija Gradečki-Poštenjak ; Hrvatski šumarski institut

Full text: croatian pdf 466 Kb

page 361-369

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Within the framework of International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests), research and chemical analyses of plant material has been carried out in Croatia on seven intensive monitoring plots with typical forest communities. In order to monitor the reliability of methods of laboratory analyses, as well as to ensure operational quality of analytical methods that can be applied in leaves and needles analysis, each year Inter-laboratory testing on samples prepared in laboratories of countries taking part in ICP Forest is organised.Croatian forest research institute, prepared leaves of common beech as reference sample for this programme that is now used also as the laboratory reference material.
In this work, the interlaboratory measurements and repeatabilty and reproducibility were tested between results of determination total nitrogen and carbon in the reference sample of common beech leaveves on elemental analyser CNS 2000 (Method A) in the laboratory of Croatina forset reserach institute and on the elemental analyser EA 300 (Method B) in the labratory of Hungarian forest institute involved ICP Forests programme.Statistical analysis included comparative description of results for determination of total nitrogen and carbon, descriptive statistics for 2 methods, Boxplot analysis, F test, T test, Regression analyses and Control charts for method B. The comparation of the results showed big oscilations of the results of Method B for nitrogen and some of them were out of specification limits. For carbon, the values were higer then in Method A (Figure 2). Furthermore, F values were over critical but variance of Method A was smaller than of Method B.Therefore, metod A was more accura-ted.For carbon, F was over critical values.Variance of method A was more significant than of method B with probability of 95 % (Table 5). Coefficient of corelation, r in regression analysis for methods (Table 6) gave positive correla-tion.With t-test (Table 7) was proved that results of these methods for determination of total nitrogen and carbon with probability of 95 % were significanty different. Control chart for nitrogen showed difference in repetability, also more than 30 % of results were out of specification limits. Repetability of reuslts forcarbon was good (Figure 4). Chemical analysis of leaves are reduced for choise of instruments and methods for determination of elements because of specificity of samples from forest. Therefore this kind of testing confirmed better applicability of element analyser such as CNS 2000 than EA 300 for determination of total nitrogen and carbon.


CNS 2000; common beech leaves; EA 300; elemental analyser; ICP Forests; interlaboratory testing; reference sample; total nitrogen and carbon

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