Parts per trillion is a highly sensitive unit of concentration used in analytical chemistry and environmental monitoring. It represents one part of a substance in one trillion parts of the total mixture, equivalent to one nanogram per kilogram or one picogram per gram. Analysts use it to quantify ultra-trace contaminants like heavy metals or persistent organic pollutants in water and soil.
Heard on the job
The mass spec picked up lead contamination at 40 PPT, well below the action limit.
Insider tip
Do not confuse PPT (parts per trillion) with ppt (parts per thousand), which is often used in oceanography for salinity. Context and capitalization usually distinguish them.