LITHIUM ION-SELECTIVE ELECTRODES EMPLOYING TETRAHYDROFURAN-BASED 16-CROWN-4 DERIVATIVES AS NEUTRAL CARRIERS

摘要

The potentiometric response characteristics of lithium ion-selective membrane electrodes employing three different THF-type 16-crown-4 derivatives as ionophores were investigated. Of the THF-based crown compounds tested, a cis-type isomer of the derivative with only methyl groups (H/CH3) at four bridged positions (cis-THF-I) was found to exhibit the best selectivity for Li+ over other cations, The composition of the cis-THF-I-based PVC-matrix membrane was optimized and its performance was compared with those based on lithium ionophores reported previously, The new cis-THF-I-based membrane exhibits remarkably enhanced selectivities for lithium over other cations: logK(Li, Na)(pot) = -2.8, logK(Li, K)(pot) = -4.6, logK(Li, NH4)(pot) = -5.4, logK(Li, Ca)(pot) = -5.7 and logK(Li, Mg)(pot) = -5.4. Furthermore, it was found that serum components do not interfere significantly with the lithium measurements when the cis-THF-I-based electrode is used, The response of the electrode was found to be linear in the clinical range of interest. [References: 41]