Mass density is the amount of mass per unit volume of a substance. Volume density is the amount of volume per unit volume. Concentration is the amount of a substance per unit volume of a mixture.

1 gpL = 1.0 kg/m^3; "gpl" stands for gram per deciliter, a unit of mass density commonly used in chemistry and medicine to measure the concentration of a substance in a solution.

1 mgpdL = 0.009999999999999998 kg/m^3; "mgpdl" stands for milligrams per deciliter, a unit used to measure concentration in solutions. It represents the mass of a substance per unit volume of 1/10th of a liter.

1 mmolGCpL = 0.18015588 kg/m^3; mmolgcpl is a unit of concentration representing millimoles of glucose per liter. It measures the amount of glucose in a given volume of a solution.