Comparison of Different Washing, Ashing, and Digestion Methods for the Analysis of Trace Elements in Vegetation

Abstract

Quantitative determination of the concentration of trace elements in vegetation is important in studies dealing with environmental impact, nutrition effects and geochemical exploration. However, the great diversity of sample preparation and analytical methods involved in the determination of trace elements in plant material makes the inter-comparison of the results reported in scientific literature difficult. The objective of this investigation was to compare the effects of different sample preparation, particularly cleaning, drying and digestion, used prior to the determination of the concentrations of ten trace elements (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in plant material. The results of the investigation suggested that the best cleaning method in studies of multi-element concentrations in vegetation is washing collected plant samples thoroughly with distilled water. Ashing at 550°C followed by digestion with a mixture of HNO₃:H₂SO₄ (2:1) appeared to be the best method for drying and digestion of the plant material. However, modifications of this technique can considerably improve the recoveries for some elements, such as arsenic and chromium.