A problem encountered in a study of the effects of lanthanide ions on enzyme-catalyzed reactions.

Investigations have been made of the time-dependent loss of the ability of dilute lanthanide solutions to inhibit creatine kinase. Using [¹⁵²Eu]Cl₃, it has been demonstrated that the loss is due to the reduction in concentration that occurs because of the adsorption of lanthanide ions onto walls of containers. Further, it has been shown that the adsorption varies with pH and the composition of the container. The results also indicate that dilute solutions of EuCl₃ do not undergo concentration changes when stored in Pyrex glass vessels either under slightly acidic conditions or in buffered solution at pH 8.0.