Pressed Powder Sample Measurements Using X-ray Fluorescence
A method of quantitative X-ray analysis includes capturing X-ray fluorescence data from a pressed powder sample including a binder. A quantity and/or distribution of binder is assumed and the concentration of various components of the sample is calculated from the measured data and the assumed quantity of binder. Then, the concentration of binder is adjusted and the calculation step repeated until the method converges. The method is allowed to take widely different values of quantity of binder, which may be the concentration of the binder in the sample or alternatively the thickness of an assumed thin layer at the surface of a model used for calculation.
1 . A quantitative X-ray analysis method, comprising:
receiving X-ray fluorescence data of a pressed sample prepared using an additional binder;
initialising an assumed quantity of binder;
calculating the concentration of a plurality of components of the sample based on the X-ray fluorescence data and the assumed quantity of binder;
changing the assumed quantity of binder based on the results of the step of calculating the concentration of a plurality of components;
repeating the step of calculating the concentration of a plurality of components of the sample and of the binder and the step of changing the assumed quantity of binder until the calculations converge; and
outputting the concentration of components of the sample.
2 . The method according to claim 1 , wherein the changed assumed concentration of binder is calculated by summing the calculated concentration of the said plurality of components and assuming that the remainder is binder.
3 . The method according to claim 1 , wherein the quantity of binder assumed is the concentration of binder in the sample.
4 . The method according to claim 3 , wherein calculating the concentration of a plurality of components includes taking into account absorbance by the binder and absorbance by the plurality of components.
5 . The method according to claim 1 wherein the quantity of binder assumed is the thickness of an assumed layer of pure binder on the surface of the pressed sample.
6 . The method according to claim 1 , wherein the quantity of binder assumed includes the thickness of an assumed layer on the surface of the pressed sample and the concentration of binder in the assumed layer.
7 . The method according to claim 1 , wherein the quantity of binder assumed includes a first quantity of binder, being the thickness of an assumed layer of binder on the surface of the pressed sample, and the second quantity of binder being the concentration of binder in the bulk in the sample.
8 . A quantitative X-ray analysis method, comprising:
forming a sample into a pellet using a binder
carrying out an X-ray fluorescence measurement; and
evaluating the results using a method according to claim 1 .
9 . An apparatus for quantitative X-ray analysis of a pressed powder sample containing a binder, comprising:
a computer containing code means adapted to cause the computer to carry out a method on X-ray fluorescence data from the pressed powder sample, the method comprising:
receiving X-ray fluorescence data of a pressed sample prepared using an additional binder;
initialising an assumed quantity of binder;
calculating the concentration of a plurality of components of the sample based on the X-ray fluorescence data and the assumed quantity of binder;
changing the assumed quantity of binder based on the results of the step of calculating the concentration of a plurality of components;
repeating the step of calculating the concentration of a plurality of components of the sample and of the binder and the step of changing the assumed quantity of binder until the calculations converge; and
outputting the concentration of components of the sample.
10 . The apparatus for quantitative X-ray analysis of a pressed powder sample containing a binder according to claim 9 , further comprising:
an X-ray source for generating X-rays and directing them to a sample; and
an X-ray detector for capturing X-ray fluorescence generated by the sample;
wherein the X-ray source and X-ray detector are connected to and controlled by the computer.