Thick-target PIGE analysis of plant materials preconcentrated by dry ashing

Plant materials were dry ashed at 550°C and analysed using particle-induced prompt gamma-ray emission (PIGE). The analyses were performed with an external beam of 3 MeV protons incident on the target. Seven biological certified reference materials were analysed and used for the evaluation of the method for Na, Mg, Al, P and Mn. The elemental concentration to detection limit ratios were greatly enhanced by dry ashing of the biological materials. The concentrations of the elements in ashes were clearly above the values at which reliable analyses can be made. The method was applied to samples of spruce and pine. Due to the low ash content of the wood samples, the sensitivity of the method was radically improved. The detection limits for the five elements studied in spruce wood were in the range 0.014–2.5 μg g−1. The set-up and the beam current used enabled simultaneous particle-induced X-ray emission spectrometry (PIXE) analyses, with the sensitivity optimised for heavier trace elements.