Double-armed crown ethers for calcium optical sensors.

Area of Science:

• Analytical Chemistry
• Materials Science
• Chemical Sensing

Background:

• Optical sensing membranes offer a non-destructive method for ion detection.
• Ionophore-chromoionophore chemistry is a key technology for developing selective chemical sensors.
• Calcium ion (Ca2+) sensing is crucial in various biological and environmental applications.

Purpose of the Study:

• To characterize optical sensing membranes for selective calcium ion detection.
• To evaluate the influence of ionophore structure on calcium selectivity.
• To determine the analytical performance of the developed calcium-selective membranes.

Main Methods:

• Synthesis and characterization of six different 18-membered crown ether derivatives as ionophores.
• Fabrication of optical sensing membranes incorporating ionophores, transducers, and plasticizers.
• Measurement of ion exchange constants (K(ILp)exch) and selectivity coefficients (k(Osel)I,J) against various interfering ions.
• Evaluation of analytical parameters for calcium determination.

Main Results:

• All studied ionophores exhibited the highest ion:ionophore stability constants for calcium ions.
• The ionophore V, featuring an (N-adamantylcarbamoyl) acetyl moiety, yielded the most selective membrane for calcium.
• Lipophilicity and terminal group size of the ionophore's side chain significantly influenced calcium selectivity.
• Calculated analytical parameters demonstrated the potential for precise calcium determination.

Conclusions:

• The developed optical sensing membranes demonstrate high selectivity and sensitivity for calcium ions.
• Ionophore V is a promising candidate for creating advanced calcium optical sensors.
• The study provides valuable insights into the structure-property relationships governing ionophore-based calcium selectivity.