The role of buffer composition during equilibrium dialysis in determining concentrations of free diazepam in serum.

Serum levels of free diazepam as determined with equilibrium dialysis depend on the composition of the dialyzing buffer with respect to Ca2+ and Cl-. Physiological concentrations of these ions double the obtained free serum levels, in line with data of diazepam containing albumin solutions. The diazepam binding capacity of serum was found to be higher than that of albumin alone, suggesting that albumin is probably not the only diazepam binding protein in serum. Evidence was also found that the diazepam binding to these other serum proteins is dependent on the presence of Ca2+ and Cl-.