Determination of partial specific volume and absolute concentration by densimetry

The apparent partial specific volume, phi, of a protein (or other macromolecule) and the absolute concentration, c, can be determined from the densimetry of solutions and diffusates in 1H2O, 2H2O and 1H2O/2H2O mixtures if the ratios of concentrations (relative concentrations) are known. The densimetry method allows a non-destructive check on total macromolecule concentrations without prior knowledge of specific u.v.-absorption coefficient. The method may be especially useful in small-angle neutron-scattering studies.