pM

picomole per liter

Molar concentrationexact by definition

The picomolar is 10⁻¹² mol/L. Antibody-antigen affinities, some steroid hormone levels and the tightest engineered binders reach it; at 1 pM a millilitre of solution holds only about 6 × 10⁸ molecules.

1 pM 1.0000000e-12 M