Low-Voltage Energy-Dispersive X-ray Microanalysis of Bulk Biological Materials

Abstract Low-voltage energy-dispersive X-ray microanalysis has a number of distinct advantages for measuring the concentration of light elements (Z = 11−20) in a largely organic matrix. Between 10 and 4 kV, there is a 50-fold decrease in the size of the incident beam-specimen interaction volume which enables discrete subcel-lular compartments to be analyzed. Experiments with mineral and organic samples of known chemical composition show that two of the most widely used analytical algorithms are capable of providing quantitative data at accelerating voltages as low as 5 kV. This technique is used at 5 kV to analyze frozen hydrated fracture faces of leaves of the tea plant which are known to contain aluminium. Higher levels of aluminium are found in the cell walls and are associated with increased levels of silicon and magnesium. The advantages and disadvantages of the experimental approach are discussed in relation to analysis carried out at higher voltages.