Influence of 4,4,4-Trifluoro-1-phenyl-1,3-butanedione on Selectivity of All-Solid-State Lithium Ion Electrode Prepared by Using 6,6-Dibenzyl-1,4,8-11-tetraoxacyclotetradecane as Ionophore and Its Application in Human Serum Analysis

In this work, we aimed to increase the selectivity of lithium selective electrodes containing lithium ionophore VI in the membrane matrix by using 4,4,4-Trifluoro-1-phenyl-1,3-butanedione (HBTA). Potentiometric response characteristics of the prepared lithium selective electrodes were investigated. Increasing the ratio of HBTA molecule in the membrane cocktail from 0.5% to 1.5% provided a better response with respect to the lower detection limit (LDL), linear range, and selectivity. The LDL and linear range of the electrode with 1.5% HBTA were 7.6x 10(-6) mol L-1 and 1.0x 10(-1) - 3.4x 10(-5) mol L-1 respectively, with a slope 54.3 mV/decade (R-2 = 0.9998). The potentiometric responses of all electrodes were pH-independent in the range of pH 3-12. The response time of the electrodes was less than 10 s and the lifetime was more than eight weeks. The electrode with 1.5% HBTA showed a better selectivity against sodium (1:575) and potassium (1:270) and was successfully applied for the determination of lithium levels in diluted human serum samples. The obtained potentiometric data were compared with the ICP-MS results at 98% confidence level.