CIANFLONE 2501XBT, Operation & Safety Manual

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5. OPERATING THE PORTASPEC
5-4
the mean count in the text file once time corrections between the two counts have
been made.
5.4. Sample Preparation and Presentation
Different Portaspec models can accept different sample sizes. The Model 2501XBT
can accept sample sizes as large as 2
–9/16 inches in diameter by 1” thick.
a. If your specimens are smaller than the x-ray port opening, a port mask must
be configured to position the specimen securely over the x-ray port.
b. If an x-ray port mask is needed, careful consideration must be taken in
selecting the mask material so to not interfere with the element under
analysis. A two-theta table and an interference chart can be found in the
appendix of this manual to aid in mask material selection.
In general, x-ray analysis involves only a thin surface layer of the sample. The x-ray
penetration will vary depending on the atomic number of the analyte and the
specimen. For qualitative analysis, identifying the elements in a specimen, the only
requirement is that the sample specimens be presented in a typical fashion.
However, when quantitative analysis is to be performed, such as how much of an
element is in a sample, more elaborate methods of specimen preparation should be
taken to ensure reproducible results.
c. For specimens too small or otherwise not suitable to use a mask, specimens
can be supported on thin films like Mylar, filter paper or even Scotch tape.
Small specimens can oftentimes be analyzed in bulk or lined side by side in
order to attain a suitable viewing area.
d. For irregular sized specimens, a typical profile must be presented or the use
of an x-ray mask may be useful here as well.
Caution: Damage can be done to the x-ray tube window or other components in the
x-ray path if a sample were to fall into the x-ray chamber.
e. All specimens that are to be compared to one another, require a typical
viewing surface in that the surface must be free from surface contamination,
flat and oriented properly.
f. If there is a grain pattern or profile on the surface to be analyzed, all
specimens must be presented in a similar manner.
g. When handling specimens, it would be a good practice to avoid touching the
surface to be analyzed.
h. The surface finish should be the same. Specimens should have the same
matrix unless mathematical corrections are to be applied to the result.
i. The amount of porosity should not vary from one specimen to another.
j. Powder specimens should be homogeneous and packed to a typical density.
k. Liquid specimens should be mixed thoroughly and put into special XRF cups
filled to at least 3/4 full. When using XRF cups, the mylar covering should be
smooth and free of convolutions that could affect the results.
l. One final consideration is the presentation of the samples at a constant
distance from the x-ray port. Large variations in the distance from the