Magnesium Ion-Selective Optodes Based on a Neutral Ionophore and a Lipophilic Cationic Dye

To whom correspondence should be addressed D.S. On leave from Department of Chemistry, Gadjah Mada University, Sekip Utara, Jogjakarta, Indonesia Flow-through type magnesium ion-selective optodes based on a neutral ionophore and a lipophilic cationic dye have been developed. The optodes were prepared by coating pellicular octadecylsilica beads with a lipophilic organic liquid containing magnesium ionophores, a lipophilic cationic dye and a lipophilic anionic additive, and packing the beads into a flow-through optical cell. Two neutral magnesium ionophores (K22B5 and K22B1B5) and two novel lipophilic cationic dyes (KDC-1 and K DC-2) were synthesized and tested for preparing the optodes. Among the developed optodes, an optode based on the ionophore K22B1B5 and a cationic dye (KDC-2) produced the best magnesium ion optode with a relatively high Mg²⁺ sensitivity and selectivity, This optode showed a fast and reproducible response to magnesium ion, even in a high concentration of background ions.