A micro-sized PVC membrane Li+-selective electrode without internal filling solution and its medical applications

A micro-sized polyvinyl chloride (PVC) membrane Li+-selective electrode without inner filling solution was constructed. The emf measurements were made by using a micro-sized solid silver/silver chloride reference electrode. The potentiometric response characteristics of the electrode were examined under steady-state conditions. The developed electrode showed high selectivity for lithium with respect to common alkali and alkaline-earth metal cations. The working concentration range of the electrode was 1.0 × 10−1 to 6.0 × 10−5 mol L−1 with a slope of 53.6 mV decade−1, and pH working range was found to be 6–10. The electrode had a very short response time (<10 s) and good reproducibility. There was no significant change in the slope of the concentration–potential curve during the usage period of 10 weeks. The developed electrode was utilized for the determination of lithium contents of human blood serum samples and pharmaceutical formulations in steady-state conditions. The obtained potentiometric results for both serum samples and pharmaceutical formulations are in good agreement with atomic emission spectrophotometry (AES) results at the 95% confidence level.