Urea electrode comprises a urease-immobilized membrane having added amino groups prepared by dipping an immobilized membrane in an aqueous solution of ethylenediamine or polylysine and an electrode for quantitative determination of ammonium ions. The electrode has a shorter measurement time with a larger...http://www.google.co.uk/patents/US4476005?utm_source=gb-gplus-sharePatent US4476005 - Urease-immobilized urea electrode and process for preparing the same
