Notes:

1. Matrix reference materials may be obtained directly from biological, environmental, or industrial sources.
2. Matrix reference materials may also be prepared by a spike of the component(s) of interest into an existing material.
3. A chemical substance dissolved in a pure solvent is not a matrix reference material.
4. Matrix reference materials are intended to be used in conjunction with the chemical analysis of real samples of the same or a similar matrix.

Examples: Soil, drinking water, metal alloys, and blood which fulfil the requirements of a reference material.