Ion-selective electrodes based on p-1-adamantylcalix[8]arene ionophores for the determination of amino compounds

The 'lower rim' functionalized derivatives of p-1-adamantylcalix[8]arene (octa(trifluoroacetyl-), L 1 , and octa(ethoxycarbonylmethoxy-), L 2 , were used as ionophores in PVC membranes of ion-selective electrodes (ISEs). The responses of electrodes towards primary amines (n-octylamine, 2-phenylethylamine) and amino acid esters are reported. The host L 1 failed as ionophore, while the L 2 -based ISE exhibited quasi-Nernstian function (with detection limits at 10 -5 M level) for n-octylamine and 2-phenylethylamine, as well as for methyl esters of phenylalanine and phenylglycine. Addition of lipophilic ionic associate tetraphenylborate-analyte was found to be useful for the enhancing of operation stability. Alkali metals and some amines practically do not affect potentiometric determination of n-octylamine and amino acid esters. In agreement with the concept of H-bonding in the host-guest complex, the interference increases in the following order : tertiary < secondary < primary amines. All ISEs studied exhibit extremely short response time (5-10 s) in wide pH and analyte concentration ranges.