Multi-element analysis of fine roots of Scots pine by total reflection x-ray fluorescence spectrometry

The aim of this work was to investigate whether total reflection x-ray fluorescence (TXRF) is a satisfactory technique for the determination of trace element concentrations in fine roots. Fine roots in diameter classes <1 and 1-2 mm from Scots pine (Pinus sylvestris L.) were used. The roots were collected at different distances from a copper-nickel smelter in south west Finland. The mass of each root sample was approximately 30 mg. The root samples were digested with nitric acid in quartz beakers at atmospheric pressure on a hot-plate. The final volume of each sample solution was 2 ml. The concentrations of P, S, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn Rb Sr and Pb were determined using TXRF. A reference material (Wood Fuel NJV 94-5) was analysed and used for quality control of the TXRF measurements. The root samples were also analysed using graphite furnace atomic absorption spectrometry (GFAAS). For most of the elements the inaccuracy was within 20% and the imprecision 4-20% for the TXRF measurements. However, for K the inaccuracy was 30% and for the elements close to the detection limits the inaccuracy and imprecision were even greater. The correlation between TXRF and GFAAS measurements was satisfactory.