Substances of Unknown or Variable composition, Complex reaction products or Biological
materials (UVCB) are substances in which:
By their very nature, UVCB substances can present a difficult analytical challenge and their characterisation may demand a somewhat different approach to that used for well-defined (mono- and multi-constituent) substances. Typical examples of UVCBs include petroleum products, plant- derived essential oils and complex inorganic species such as synthetic minerals.
Formal substance identification involves several elements:
Substance identity is often defined by the commercial sector within which each UVCB is produced and marketed. Formal quality standards are usually set that must be fulfilled in order for a substance to be sold for a given application. This usually includes at least some analytical information that could be used as a point of reference.