Optical sensor for sodium based on ion-pair extraction and fluorescence

✍ Scribed by Z Zhujun; J.L Mullin; W.R Seitz

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 572 KB
• Volume: 184
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/s0003-2670(00)86489-2

✦ Synopsis

A reagent phase that responds to sodium ion is used in a sodium-selective fiber-optic sensor. The components of the reagent phase are the ammonium salt of &anilino-lnaphthalenesulfonic acid (ANS), copper( II)-polyethyleneimine, and a commercial sodium-selective ionophore [N, N', N"-triheptyl-N, N', N"-trimethyl-4,4',4"-propylidynetris(3-oxabutyramide)] immobilized on silica. In the absence of sodium, the ANS binds to the copper(I1) polyelectrolyte and fluorescence is quenched. When sodium (20-200 mM) is added, it forms a cationic complex which forms ion-pairs with some of the ANS, causing it to fluoresce. Response is linear at the lower sodium concentrations but tends to curve toward the concentration axis at higher concentrations. The sensitivity and the range of linear response depend on ANS concentration. Typically, it takes l-3 min to reach 90% of steady-state response. The response time increases with decreasing temperature, increasing amounts of immobilized ionophore, and higher sodium concentrations. The selectivity of the sensor is established by the selectivity of the ionophore.