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Only a small sample (1-2 gram) is needed for element measurement, and therefore it is very important that the laboratory sample is representative for the food being analyzed. To be able to take a representative homogeneous sample, solid foods are most often cut, dried and then finally ground.

Contamination

A potential problem is contamination by elements released from the equipment used during sample preparation (e.g. grinding). Because the element content of foods is often low, contamination can have a large impact. Potential sources of contamination include: repeatedly used glassware; grinders, or the quality of water used in sample preparation. It is recommended to use distilled-deionised water when preparing samples.

The table below shows an example of sample contamination of barley due to the use of different mills for grinding. Mill A (made of iron) leads to contamination with iron and resulted in elevated iron values. Mill B (made of aluminium) resulted in elevated aluminium values (Average values are presented; standard deviation in brackets).