The XRF method of heavy metal analysis with an energy dispersive X-ray
spectrometer based on a semi-conductive Si (Li) detector is proposed for
toxicological studies. An excitation sources are Mo anode X-ray tube with
Johan-curved crystal monochromator or isotope source 241Am. There are two kinds
of XRF-installations - for macro-samples and for micro-samples analysis.
Based on previous experience, the proposed sample selection, preparing and
analysis scheme is such.
A samples mast be carefully marked and must to contain a minimal quantity of
mineral components. Precise coordinates of sample collection place are require.
It is desirable to dry a samples at the temperature of ~600C. Humid samples rot
and decay partially at a long transportation.
A sample mass must to provide an ashes sample mass not less then 200 mg.
Taking into account a cremate degree and a possible partial losses, a feather
samples mass mast not be less then 10 g of dry substances.
A special attention is required to guano samples. The previous studies show a
grate concentration of microelements in it. It allows to analyze a such samples
by XRF-method without ashes.
A sample mass in that case may be smaller (near 1
mg or less), but it is a very important to avoid a small stone and sand
admixture. Also an additional investigation of typical nature and homogeneity of
such micro-samples may be necessary.
A possibility of a sample washing by distillate water is required to test from point of view a micro-element loss.
The ordinary further sample preparation and analysis at a laboratory:
1.Drying at the temperature of 1000oC and weighing.
2.Previous low temperature (200-300oC) ashes, weighing and homogenization
(reducing and mixing). A mineral components (small stone, sand) careful
rejection.
3.Step by step (every 100oC, up to 1000oC) ashes, weighing and analysis in
order to element loss control.
An authors express one's thanks to the INTAS for support of this research (INTAS project 01-0517).
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