Understanding Partitioning in a Cell

When species mass enters a Cell, it is instantaneously partitioned among the media present in the Cell. The partitioning is controlled by the partition coefficients defined for each species in each medium, and the quantity of each medium present. In particular, in the absence of solubility limits, the concentration of species i in Medium x is computed by GoldSim as follows:

where:

c_xi	=	concentration of species i in medium x in the cell [(M/L³) for Fluids or (M/M) for Solids];
m_i	=	mass of species i in the cell [M];
K_xi	=	partition coefficient between medium x and Reference Fluid for species i [(L³ /L³) for Fluids or (L³/M) for Solids];
K_gi	=	partition coefficient between medium g and Reference Fluid for species i [(L³ /L³) for Fluids or (L³/M) for Solids];
VM_g	=	quantity (volume or mass) of medium g in the cell [L³ for Fluids or M for Solids]; and
NM	=	the number of media in cell.

Note that, by definition, for all species the partition coefficient between the Reference Fluid and itself is 1 (i.e., in the above equation, if x is the Reference Fluid, K_xi = 1).

Note: If the partition coefficients are defined as being independent of the concentration of the species (at a given temperature), the concentrations then vary linearly with mass in the cell (assuming no solubility constraints). This relationship is referred to as a linear isotherm. Non-linear isotherms, in which the degree of partitioning varies with concentration, can be readily represented in GoldSim by defining the partition coefficients as functions of the concentrations.