Monte Carlo simulation for an assessment of standard validity and quantitative X-ray microanalysis in plants

Protein matrices with known concentration of elements are used as standards in X-ray microanalysis of biological materials. The aim of the study was to assess if protein standards (gelatine) could be applied for quantitative X-ray microanalysis of carbohydrate material (cellulose) of plant cell walls by means of Monte Carlo simulations. Plant roots grown in Cs contaminated soil and gelatine with known elemental concentration were prepared according to freeze-drying protocols. The atomic fractions of gelatine and cellulose were used to simulate spectra and than compared to experimental ones. There was a good agreement in bremsstrahlung generation between gelatine and cellulose matrices. The experimental and simulated spectra of gelatine revealed a difference in background shape at low energies but corrected if specimen was tilted to -10° or the matrix density increased to 0.95 g/cm. Minimum detection limit (MDL) simulated for Cs Lα in cellulose was also in agreement with that experimentally calculated for gelatine standard. Protein standard resembles carbohydrate materials and can be used for quantitative analysis of plant cell walls. However, using Monte Carlo simulations to predict analytical conditions for biological materials and elemental MDL, differences in topography and/or gelatine densities should be taken into consideration.