Development and application of a fluorescent sensor for potassium ions based on a calix[6]arene ionophore and a novel cationic dye

A plasticised poly(vinyl chloride) optode membrane incorporated with a calix[6]arene hexaester, a H⁺-selective chromoionophore (3,3′,5,5′-tetramethyl-N,N-dibenzylbenzidine, a novel synthetic cationic dye) and a lipophilic potassium tetrakis(4-chlorophenyl)borate was used as a sensing device for the indirect optical determination of potassium ions. It exhibited a reversible response to the potassium ion in 0.05 mol/l HCl buffer media in the concentration range from 1 × 10^-6 to 1 × 10^-2 mol/l. The linear range was from 1.53 × 10^-5 to 3.20 × 10^-3 mol/l. The proposed optode sensor exhibited a fast response of less than 1 min, good repeatability (n 1/4 7, RSD 1/4 3.62%) at 5 × 10^-5 mol/l, and long-term stability with 92% of its initial sensitivity after 1 month of storage. The selectivity of the potassium-selective membrane allows its application for the detection of the potassium concentration in real sample analysis. The result was satisfactory compared with atomic absorption spectrometry.