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Sample preparation
for XRF analysis offood products, animal feed,premixes and related materials

Food and animal feed samples are heterogeneousmaterials with many of the same elements distributed into
various constituents like protein, fat and carbohydrate-richphases. A proper sample preparation technique will help
you determine reproducible and representative elementalcontent.
Grinding and pressing might be difficult or even impossible
to perform due to oily or sticky sample characteristics. Youmight have to follow special procedures. Good news: theseprocedures are normally easy to implement using available
specialized equipment.
Mineral premixes are typically inorganic samples which caneasily be prepared as pressed pellets or glass disks.

Loose powder/liquid cups
You can analyze powdered/homogeneous materials
directly in loose powder cups (liquid cups) especiallywhen the sample must be recovered or when accuracy/
reproducibility are not the main drivers.
Any liquid or semi-solid samples (solutions, emulsions,slurries, etc.) can be analyzed in liquid cups. No further
preparation is needed! However, you must ensure thatthese samples are stable and that they will not segregate
during the analysis.
Malvern Panalytical offers dedicated and single-use sample
cups in 32 or 40 mm diameter, with corresponding lids.
These cups are carefully designed with high standards inproduction control. They are safe to use and ensure thatyou will get the best analytical conditions for any liquid (orloose powder) samples.

Grinding
It is necessary to grind dry and brittle samples into a fine
powder to minimize undesired particle size effects andallow further processing like pressing or fusion.

Cutting, blending & homogenizing
Moist, fatty or soft samples (including fresh produce orother plant-/ animal-derived substances) may require
cutting into fine particles or blending into a homogeneous

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slurry. Cutting or knife mills or high-power specialized lab
blenders are then useful. Samples processed in such a way
can be conveniently pressed into pellets or presented tothe XRF spectrometer in a liquid cup.

Pressing
As a general rule, pressed samples deliver more accurate
and reproducible results than loose powders in cups.
Detection limits are also lower, as there are no absorption
losses due to the cup’s foil.
Pellets can be pressed freely into Al cups or steel rings.
Cellulose or protein-rich samples may be pressed as is,but mineral-rich samples may require the use of binders toachieve the necessary mechanical stability and robustness.

FusionYou can prepare mineral-rich samples or calcined residues
as glass disks. When accuracy and reproducibility play asignificant role, this is arguably the best way to present
a sample. With Malvern Panalytical automated fusion
instruments, you dissolve the sample into a molten glassforming flux at high temperatures, and it ultimately results
in a completely homogeneous glass disk. This way, particle
size and matrix effects are eliminated.
It is difficult to obtain suitable standards that have thesame particle size, mineralogy, surface roughness andsegregation characteristics as the production samples.
Therefore, the role of glass disks is extremely important insetting up reference calibrations for determining in-housestandards for the production of control calibrations.

Handling oily samples
Materials with high fat content require special care during
grinding and pressing to avoid the mobilization of thefat as well as clumping and segregation of the sample.
This is why you will need an additive for oily samples. It
will guarantee that fatty components are not mobilized
during normal grinding and pressing, leading to anincreased sample preparation repeatability, accuracy andrepresentativeness of results.

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