| dc.description.abstract | The utility of Energy Dispersive X-ray Fluorescence (EDXRfo) spectrometry has revealed
that accurate trace clement analysis in light clement matrices is limited by scattering and the
associated high background radiations; which complicate the empirical relationship he tween the
analyte fluorescent line intensities and the corresponding concentrations for the elements or
interest.
A survey of the relevant literature however, shows that scattered and background radiation
provides for matrix correction and dark matrix modelling of light element matrices.
It has been found that in EDXRfo analysis of light element matrices, the main background
is from backscatter. which may be attributed to the photoelectrons in the sample itse] 1'; which
artsc Irorn the matrix atoms. Photons of energies less than the Rayleigh scattering arc produced
which conuibutc to background throughout the energy spectrum used for analysis. Appropriate
mathcmat icn] luncfions. which account for low-energy background, are therefore desirable to
describe background distribution and scattering in a light element matrix.
The background distribution functions of light element matrix fluorescence responses
obtained with (1 '()f)ed radioisotope excitation source have been studied in order to optimize for
spec t1'(11 stripping and anaIysis. The background was estimated by measuring the noise lcvc Is to
hol h sides of the spectral photopeaks, which were then optimally filled with various linear anc]
nou-Iinenr functions using /\XIL-QX/\S.
This study has shown that background and scattering in plant material analysis hy XI~F
spectroscopy is mainly due to the carbon matrix. Up to the Dr- Kfl line. low-energy physical
phcnomeua in the sample mauix dominate the background distribution. In the region between the
Br- K" and the 7r- Ka line energies. a linear relation is sufficient; and beyond this region. the
background rapidly rises to fit exponential functions. The various background modelling functions
til:ll were deduced in the encrgy regime 3.313 KeY to 15.746 KeY have been applied in the
Analysis of I.A.E.A soil-7 certified reference standard to accuracies or ~ (± 5) % in concentration
estimates for appropriately optimized spectral lines.
elemental analyses 0(' selected samples whose supporting matrices are made up 0(' light
clements was then performed by studying and optimizing the spectrometer Ior the followiuj;
parameters: detection limits (DL), signal to noise ratio (SNR), elemental sensitivity (S), spectral
1:!JltIssinll symmetry and background spectral fitting functions. Statistical considerations show that
these performance indices depend on the stochastic process or the X-ray signal detection and
processing. and therefore heavily influence light element matrix analysis. The K-series spectral
lines were used for analyses or elements with Z ~ 40 and the L-series spectral lines for clements
with 7, 2': 55. Different types or rock samples; standard I.A.E.A certified reference samples:
prepared standard stock solutions; Arabica and RO/JIIs/n coffee beans, their leaves and soils on | en |
