High-Acidity Determination in Salt-Containing Acids by Optical Sensors. The Scope of a Dual-Transducer Approach and the Hammett Acidity Function

• Published in: Analytical chemistry (Washington) Vol. 74; no. 11; pp. 2535 - 2540
• Main Authors: Canada, T. Andrew, Allain, Leonardo R, Beach, David B, Xue, Ziling
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.06.2002
• Subjects: Acids; Analytical chemistry; Chemistry; Exact sciences and technology; General, instrumentation; Salt; Sensors; Salt; Hammett function; Multicomponent analysis; Azine dye; Ionic strength; Triarylmethane dye; Color indicator; Optical sensor; Strong acid; Chemical sensor; Neutral red
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac0200623

A dual-transducer approach based on sol−gel optical sensors was recently reported to measure acid and salt concentrations, C acid and C salt, in concentrated aqueous LiCl−HCl, CaCl2−HCl, and AlCl3−HCl solutions (C acid at 5−6 M; C salt ≤ 2 M). The scope of this new approach has been studied in salt-containing HCl solutions with C acid at 2−9 M, and factors that influence sensor responses and accuracy have been investigated. A linear relationship between (∂A/∂C salt) C acid and (dA/dC acid) C salt=0 , which is the basis of this dual-transducer approach, was found to lead to an empirical linear relationship between (ΔH 0) C acid and (ΔC salt) C acid (H 0:  Hammett acidity function of the indicator encapsulated in the sensor).