A fluorescent chemosensor for calcium with excellent storage stability in water

This article describes the design, synthesis and characterization of an optical sensor suitable for practical measurement of ionized calcium in serum and whole blood samples. The key to the development of this sensor is the identification of a chemically very stable, nitrogen-containing, calcium selective ionophore, coupled with a fluorophore having the correct spectral and electron accepting properties. The slope of the sensor is about 34%/mM in the typical clinically significant range of 0.32-2.2 mM. This sensor has been implemented into the disposable cartridge, used for commercially available OPTI CCA analyzer with precision better than ±0.02 mM (1 S.D.). The sensor displays excellent stability against hydrolysis and oxidation, leading to less than 0.02 mM measurement error after 9 months of wet storage at room temperature, up to 30 °C.