Metallation of complexing agents with lanthanides and use as contrast agents

摘要

A process for the preparation of a lanthanide complex by reaction of a lanthanide oxide with a complexing agent, ie DTPA-BMN, in an aqueous reaction medium. The process comprises the steps of: a) determining the level of impurity in the lanthanide oxide, and b) mixing a lanthanide oxide from batches with different determined levels of impurity and/or including in the reaction medium a ore-determined quantity of oxalic acid, salt or derivative thereof. The reagents used in the metallation reaction contain oxalic acid or oxalate at a total level of at least 50ìg oxalic acid per gram lanthanide oxide.