concentration unit gram per liter http://www.ebi.ac.uk/efo/EFO_0001810 UO_0000175 A gram per liter is a density unit which is equal to mass of an object in grams divided by the volume in liters. Jon Ison http://www.ebi.ac.uk/efo/EFO_0004372 A mass unit density which is equal to mass of an object in grams divided by the volume in liters. SNOMEDCT:258794004 g/L James Malone density unit