The main objective of sampling consists in obtaining representative samples of the compound to be analysed (water, sludge, grease, sand, reagents, materials, gases …). For instance the sampling method will not always be the same depending on whether we are dealing with the element to be analysed is in the solid, liquid or gas state.
The sample concerned may be:
- grab or instantaneous (randomely collected throughout the day);
- composite or proportional (two or more samples combined in known and appropriate proportions appropriate proportions to obtain an average value) in relation to time, flow rate or any other variable.
Different sampling standards apply depending on the type of element to be analysed. These standards are listed in ISO 5667.