Lithium salts such as Li2CO3 have been used as a medicine for manic depressive and hyperthyroidism patients.'The Li+ concentration in the serum of manic depressive patients was reported to be 0.5-1.5 mM, with over 1.5 mM being a toxic range.'Thus, a Li+ sensor for monitoring Li+ in blood fluids is desired in the medical and clinical fields in order to monitor and control the Li+ concentration in the human body. For blood serum analysis, a high ...