δ¹⁸O (delta-18 O) refers to the ratio of two stable oxygen isotopes: ¹⁸O:¹⁶O. Each contains eight protons with the former containing ten neutrons and the latter, eight neutrons. δ¹⁸O analysis, also referred to as isotopic signature, takes advantage of how environmental variation differentially affects the relative abundance of each isotope in the signature. δ¹⁸O measurements can help inform agricultural soil science, ecology, ocean science, hydrology, paleontology, and the food & beverage industry.

For example, these signatures can be used to help identify groundwater’s source by exposing its interaction with minerals. Similarly, δ¹⁸O analysis can reveal the geographical provenance of a food (e.g. apples) or whether or not a product branded as 100% homogenous (e.g. 100% olive oil) has been diluted. δ¹⁸O can also be used to provide information on past water temperatures, for example, from shells of certain marine organisms.

Picarro has designed and produced several isotope analyzers that precisely measure δ¹⁸O in water for laboratory and field studies.