Comparison between two dry mineralisation methods (with and without HF) of palm leaves for determination of potassium-influence of silica
1997
Heral-Llimous, Gisèle | Fallavier, Paul
Many possibilities exist for the preparation of plant samples for elemental analyses, each having its merits and disadvantages. Wet acid digestion presents several drawbacks, such as potential risk of explosion when using perchloric acid, corrosion of apparatus, and contamination by elements from acids, therefore dry ashing is preferred for routine analyses. In this paper, dry ashing without hydrofluoric acid (HF) which provides insolubil- ization of silica (Si02) is compared to dry ashing with HF (CII-Method) which eliminates silicon by the evaporation of SiF4, For samples rich in silica, such as oil palm leaves, the mineralization without HF gives lower results for calcium (Ca), magnesium (Mg) and above all potassium (K) as compared to results using the HF process. Silica present in botanical materials may form insoluble silicates, and therefore retain elements by adsorption. This study dealt with the relationship between the level of silica in palm leaves and the precision of the determination of K by inductively coupled plasma (ICP) emission spectrometry, The correlations indicated that equivalent results are obtained by the two methods when the level of silica in the leaves is lower than 3.5fb (dry matter). Above that level, when using the method without HF, the decrease in K content determined increases proportionally with the silica level in the sample and can reach as much as 17fb for a K value at 0.6fb. (Résumé d'auteur)
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