Hydrophilic sensor membrane based on cation-selective protic chromoionophore

The first potassium optode based on a protic chromoionophore immobilized in a hydrogel matrix is presented. The highly selective protic chromoionophor e consists of a cryptohemispherand moiety and a trinitroanilino chromophore part. The acidifying power of potassium ions over sodium ions is 0.6 pH un its. This correlates with the findings in solution. In contrast to several crown and ate-crown based chromophores the highly preorganized moiety allow s ion detection even in aqueous environment. The detection limit for potass ium ions at pH 7.7 is 5 mu M.