Some Perspective on 10-18 nmol/mL

1 x 10-18 nmole/mL is tiny. There are per mole 6.25 x 1023 molecules. 10-18 nmol/mL = 10-18 x 10-9 = 10-27 mole/mL = 10-27 x 6.25 x 1023 molecules/mL = 6.25 x 10-4 molecules/mL = 0.625 molecules/L. For a human being of 80 kg (roughly 80 liters), this means a skin penetration of 0.625 x 80 = 50 molecules per square centimeter in a normal human body.