Ultra-High-Sensitive Extraction-Photometric Determination of Sodium Ion Using Flow Injection Analysis with a Chromogenic Calix[4]arene Derivative and a Laser Interferometric Photothermal Detector

A novel flow injection analysis (FIA) system for ultra-high-sensitive determination of Na+, which involves laser interferometric photothermal equipment as the detector, was designed using a proton-dissociable chromogenic calix[4]arene derivative with a dinitrophenol moiety as the extraction-photometric reagent. The chromogenic calix[4]arene derivative showed an excellent extractability toward Na+, which reflected the cation-complexing property of the tetraethyl ester derivative of calix[4]arene. As the calibration graph of the Na+ concentration could be successfully obtained at the nanomolar level by this method, the proposed FIA system was found to be promising for highly sensitive determination of Na+ in very dilute samples such as supply water and cooling water in power plants.