pmolL

pmol/L, or picomoles per liter, is a unit of molar concentration used to express the amount of a substance in a liter of solution. It represents a very small concentration: one picomole (10^-12 moles) of solute in one liter of solution. In practice, 1 pmol/L is equivalent to 1 pM (picomolar) when written in shorthand.

The unit is widely used in biochemistry, clinical chemistry, and environmental science to report low-abundance compounds such as hormones, cytokines, signaling molecules, metabolites, and nucleic acids in blood, serum, plasma, urine, or cell culture media. Because many biological molecules are active at picomolar levels, pmol/L provides a convenient and standardized way to describe their concentrations.

Converting pmol/L to mass concentration depends on the solute’s molar mass. If a substance has molar mass M g/mol, then its concentration in ng/L is c × M × 0.001, where c is the concentration in pmol/L. For example, a 100,000 g/mol protein at 1 pmol/L corresponds to about 100 ng/L. Conversely, to convert ng/L to pmol/L, use pmol/L = ng/L ÷ (M × 0.001).

Common measurement techniques include highly sensitive immunoassays (e.g., ELISA), liquid chromatography–tandem mass spectrometry (LC-MS/MS), and other analytical methods designed to detect trace levels. Precise reporting typically uses pmol/L or pM, with attention to consistency across assays and literature.