All-Solid-State Polyvinyl Chloride Membrane Lithium-Selective Electrode with Improved Selectivity and Its Application in Serum Lithium Assay

Abstract

A new miniaturized all-solid-state polyvinyl chloride (PVC) membrane Lit-selective electrode with extra ten-fold improved Li-selectivity towards Na+ has been described. The selectivity of the membrane contained 6,6-dibenzyl-1,4,8-11-tetraoxosiclotetradecane was improved with the addition of Trioctylphosphine oxide (TOPO). The effect of TOPO ratio in the electrode membrane was examined under steady-state conditions. The electrode containing TOPO at the ratio of 1.0% performed best potentiometric properties for the serum Li+ assays. The proposed TOPO-embedded Li+-selective electrodes with improved selectivity (lithium to sodium; 1:1000) had a wide concentration range of 2.7 x 10(-6) 1.0 x 10(-1) M and a slope of 47.6 mV/decade (R-2 = 0.9981). The developed electrode was analytically applied for the determination of lithium contents of diluted human serum samples by using direct and standard addition measurement methods. The obtained potentiometric results for the serum samples with the proposed electrode were confirmed by atomic absorption spectrophotometry (AAS) results at 95% confidence level.